While I typically associate blueberry desserts with spring and summer, this Keto Blueberry Spice Cake would make a lovely finale any time of the year. Made with fresh blueberries, cinnamon, and freshly grated nutmeg, this tasty cake is then coated with a luscious Blueberry Mascarpone Frosting.
Let me tell you about one of the things I rarely do–make layer cakes. I like them better than flat cakes, find that they often have more interesting flavors going on, and infinitely prefer the double layers of frosting. However, I’m intimidated every time by the prospect of appropriately greasing the cake pans so that I can de-pan them without incident. Even knowing that I really should be past this by now, I usually just take the path of least resistance and bake a cake in a pan from which I do not need to remove it.
Well, I concluded that this Keto Blueberry Spice Cake deserved the two layer treatment. Okay, really, I wanted an excuse to use more of the Blueberry Mascarpone Frosting. Trust me; it’s worth it. While I can happily eat the frosting with a spoon, even my friends might give me strange looks if I just serve frosting for dessert.
What You Need to Make Keto Blueberry Spice Cake
Equipment
- Stand Mixer or Hand Mixer and Large Mixing Bowl
- Large Mixing Bowl
- Measuring Cups
- Measuring Spoons
- Fine Mesh Strainer – For sifting the Almond Flour
- Rubber Scraper
- Parchment Paper
- Nonstick Cooking Spray
- 2 9-inch Round Cake Pans
- Cooling Rack
- Cake Rounds – Optional. This is really just to make it easier for you to move the cake around once you frost it.
- Cake Stand – Optional. This is just to make it easier for you to frost the cake. Sometime I’ll have to show you the comedy of errors that I experienced when working without a good place to ice / frost a cake.
- Cake Saver – Optional. I like being able to cover my cakes whenever they are not actively being served. That holds true when I have it in the fridge, on the counter, or on the serving table.
Ingredients
For the Blueberry Spice Cake:
- Unsalted Butter – Softened
- Sweeteners – See my notes below on why I selected the combination that I did.
- Granulated Erythritol
- SoNourished Gold – Or another brown erythritol or brown sugar substitute of your choice.
- Allulose
- Eggs – I use jumbo eggs.
- Sour Cream
- Vanilla Extract
- Cinnamon
- Nutmeg – Freshly Grated
- Almond Flour – I recommend taking the extra minute to sift it. Just use a fine mesh strainer and not one of the traditional hand sifters that you might use for regular flour. Almond flour has more moisture in it and tends to clump in the regular sifter.
- Unflavored Whey Protein Powder – While I suspect you could use egg protein powder, I have not tested that substitution and so can’t vouch for it..
- Baking Powder
- Kosher Salt
- Blueberries – I use the amount listed and then some more for topping / garnish.
For the Blueberry Mascarpone Frosting:
- Heavy Cream
- Mascarpone Cheese
- Allulose – In my little sweetener explanation below, I include an explicit note about the use of allulose in the frosting.
- Vanilla Extract
- Blueberries – As noted above, I use the amount listed and then have more for topping.
Getting Started with Making Keto Blueberry Spice Cake
We’ll approach making this Keto Blueberry Spice Cake in three parts:
- Making and Baking the Blueberry Spice Cakes
- Making the Blueberry Mascarpone Frosting
- Assembling the Cake
Layer Cake vs. Single Layer Cake
I like the look of this cake in its layered format. However, if you’d rather make it in a single pan, that’s fine. I’d use a 9×13-inch cake pan. While I have not tested the baking time in that format, I would suggest starting with 20 minutes, checking it, and increasing from that point. I suspect it will be closer to 28-30 minutes. If you try it, please feel free to add your findings in the comments.
A Note on the Sweeteners
The choice to use three sweeteners in this cake is deliberate. I like this overview of keto sweeteners from All Day I Dream About Food for more of a deep dive on the topic. However, my reasons are as follows:
- Granulated Erythritol – Adds sweetness, bulk, and crystallization structure. It can have a bit of a cooling effect in large quantities that is not a favorite of some of my regular guests.
- Brown Monk Fruit & Erythritol Blend – I like the more nuanced flavor that comes with the brown sugar substitutes. I have been particularly a fan of the SoNourished Gold lately which happens to be a monk fruit and erythritol blend.
- Allulose – Allulose doesn’t recrystallize like erythritol does. So while it adds bulk, it keeps things soft and doesn’t contribute as much to the structure. I wanted this one for its sweetness without the cooling effect of the erythritol. However, I have read but not personally experienced that it can cause more gastrointestinal discomfort. For that reason, I didn’t want to use only allulose.
In short, you could substitute other sweeteners if you prefer.
A particular note for the Blueberry Mascarpone Frosting: If you use an erythritol based sweetener in place of the allulose, it will harden (i.e. crystallize) a bit as it sets and there will be some cooling effect. This will be more noticeable in the frosting than in the cake itself.
Making the Cakes
Prep for Baking
Before we start cooking, we’ll get everything set up for baking by preheating the oven to 325°F and preparing two 9-inch cake pans. Because I really want these cakes to be easy to remove from their pans, we’re going to do some non-stick overkill. First, you’ll lightly spray them with nonstick cooking spray. Then, you’ll line them with parchment paper. Finally, you’ll spray the parchment paper with nonstick cooking spray.
Mixing the Wet Ingredients
In a stand mixer or large mixing bowl, we’ll beat ½ cup of softened Unsalted Butter with ¼ cup of Granulated Erythritol, ¼ cup SoNourished Gold (or other brown sugar substitute of your choice), and ¼ cup of Allulose until the mixture has lightened (about 2 – 3 minutes).
Then we’ll beat in 3 Eggs (I use jumbo), one at a time, until they are all incorporated. After that, we’ll add ¼ of cup Sour Cream, 1 teaspoon of Vanilla Extract, ½ teaspoon of Cinnamon, and ½ teaspoon of freshly grated Nutmeg and beat it until combined.
Combining the Dry Ingredients
While that’s happening, we can move on to dry ingredients. In a separate bowl, we’ll sift 2.25 cups of Almond Flour, ⅓ cup of Unflavored Whey Protein Powder, 1 tablespoon of Baking Powder, and ¼ teaspoon of Kosher Salt. Yes, I really do recommend sifting the Almond Flour. You can get away with not doing so, but your cake texture will be improved if you do.
Incorporating the Wet and Dry Ingredients
Now, we can add the dry ingredients into the wet, working in 2 installments and mixing after each addition. Then, using a rubber scraper or spatula, we’ll fold in 1 cup of Blueberries. While you can expect a few to break, we’re trying to be gentle and keep as many of them whole as possible.
Baking and Cooling the Keto Blueberry Spice Cakes
With the batter ready, we can pour half of it into each of the prepared cake pans. Then we’ll bake the cakes at 325°F for 20 – 25 minutes or until a toothpick inserted in the center comes out clean. Once done, you’ll remove the cakes to a cooling rack and allow them to cool completely.
Making the Blueberry Mascarpone Frosting
I like to think of this as the fun part, but maybe that’s just because I always get to lick the bowl.
We’ll start the Blueberry Mascarpone Frosting by whipping 2 cups of Heavy Cream in a stand mixer or mixing bowl until they reach stiff peaks. Then you’ll set this whipped cream aside. If you have a second bowl for your mixer, you can just leave it as-is and swap bowls. If not, you can spoon / spatula the whipped cream into another bowl for temporary holding.
Then, you’ll beat 16 ounces of Mascarpone Cheese with 1 cup of Allulose and 2 teaspoons of Vanilla Extract. Once combined, you can add 1 cup of Blueberries and continue beating. In this case, we’re not trying to keep the blueberries whole. We want the beater to mash them into the mixture.
Now we’ll begin combining the whipped cream into the mascarpone mixture by spooning about a quarter of the whipped cream into the cheese and folding it in. This will help to lighten it up a bit. Then you can fold a third of the remaining whipped cream into the mascarpone mixture. You’ll continue folding the rest of the whipped cream, continuing to work in thirds.
Once combined, you’re ready to frost.
Assembling the Keto Blueberry Spice Cake
Okay, I suspect that true bakers may gasp in horror at a few of my next steps. To any of you out there, I apologize.
We’ll start our cake assembly by placing the flat bottom of one of the cooled cakes onto a cake round or whatever plate or flat surface you will be using while you frost the cake.
Here’s the horrifying part: we’re not going to level either cake. Maybe someday, but today is not that day. We’re also not bothering with a crumb coat. 🤷
You’ll want to spoon about a quarter of the frosting onto the cake. I start in the middle and spread out from there. This should be a nice, thick layer of frosting.
Then, you’ll flip the second cake upside down so that the flat bottom is facing up, again without leveling. (I’m pretty sure that should be gasp #2.) Now, you’ll spoon more of the frosting on top in the middle. Again, you’ll gently spread the frosting out from the middle. Then you can move on to frosting the sides. After that, I do another swipe on top and try to even things out and cover any challenging spots, particularly along the seam.
Finally, you can sprinkle a handful of blueberries on top for garnish.
Storing this Keto Blueberry Spice Cake with Blueberry Mascarpone Frosting
Due to the creamy, cheesy nature of the frosting, I suggest storing this cake in the fridge if you are not going to be serving it in the relatively near future or if your house / location is on the warmer side.
Related Recipes
Looking for some other desserts in the “berry” theme of things? You might like one of these:
Maybe you need the rest of a menu to go with this Keto Blueberry Spice Cake? If so, check out my Cheese Day Dinner Party post for some ideas.
Still have cake on the brain? Try my Easy Keto Carrot Cake.
Keto Blueberry Spice Cake
Ingredients
For the Blueberry Spice Cake:
- ½ cup Unsalted Butter Softened
- ¼ cup Granulated Erythritol
- ¼ cup SoNourished Gold Or another brown erythritol or brown sugar substitute of your choice
- ¼ cup Allulose
- 3 Eggs Room Temperature
- ¼ cup Sour Cream
- 1 teaspoon Vanilla Extract
- ½ teaspoon Cinnamon
- ½ teaspoon Nutmeg Freshly Grated
- 2 ¼ cups Almond Flour
- ⅓ cup Unflavored Whey Protein Powder
- 1 tablespoon Baking Powder
- ¼ teaspoon Kosher Salt
- 1 cup Blueberries plus more for topping
For the Blueberry Mascarpone Frosting:
- 2 cups Heavy Cream
- 16 ounces Mascarpone Cheese
- 1 cup Allulose
- 2 teaspoons Vanilla Extract
- 1 cup Blueberries
Instructions
To Make the Blueberry Spice Cakes:
- Preheat the oven to 325°F and prepare two 9-inch cake pans by lightly spraying them with nonstick cooking spray, lining them with parchment paper, and then spraying that with nonstick cooking spray.
- In a stand mixer or large mixing bowl beat ½ cup Unsalted Butter (softened), ¼ cup Granulated Erythritol, ¼ cup SoNourished Gold, and ¼ cup Allulose until the mixture has lightened. (About 2 – 3 minutes.)½ cup Unsalted Butter, ¼ cup Granulated Erythritol, ¼ cup SoNourished Gold, ¼ cup Allulose
- Beat in 3 Eggs, one at a time, until incorporated. Then add ¼ cup Sour Cream, 1 teaspoon Vanilla Extract, ½ teaspoon Cinnamon, and ½ teaspoon Nutmeg (Freshly Grated) and beat until combined.3 Eggs, ¼ cup Sour Cream, 1 teaspoon Vanilla Extract, ½ teaspoon Cinnamon, ½ teaspoon Nutmeg
- In a separate bowl, sift 2 ¼ cups Almond Flour, ⅓ cup Unflavored Whey Protein Powder, 1 tablespoon Baking Powder, and ¼ teaspoon Kosher Salt.2 ¼ cups Almond Flour, ⅓ cup Unflavored Whey Protein Powder, 1 tablespoon Baking Powder, ¼ teaspoon Kosher Salt
- Add the dry ingredients into the wet in 2 installments, mixing after each addition.
- Fold in 1 cup Blueberries.1 cup Blueberries
- Pour half of the batter into each of the prepared cake pans.
- Bake at 325°F for 20 – 25 minutes or until a toothpick inserted in the center comes out clean.
- Remove the cakes to a cooling rack and allow them to cool completely.
To Make the Blueberry Mascarpone Frosting:
- Place 2 cups Heavy Cream in a stand mixer or large mixing bowl and whip to stiff peaks. Set it aside either in a separate bowl or leave it in the same one if you have multiple bowls for your stand mixer. .2 cups Heavy Cream
- In the stand mixer or large mixing bowl, beat 16 ounces Mascarpone Cheese, 1 cup Allulose, and 2 teaspoons Vanilla Extract.16 ounces Mascarpone Cheese, 1 cup Allulose, 2 teaspoons Vanilla Extract
- Once the mixture is homogeneous, beat in 1 cup Blueberries.1 cup Blueberries
- Fold approximately one quarter of the whipped cream into the mascarpone mixture. Then incorporate the remaining whipped cream, working in thirds, until the mixture is fully combined.
- Set it aside while you set up for frosting the cake.
Assembling the Cake:
- Place 1 of the cakes flat side down on a cake round and / or whichever flat surface you’re using for icing.
- Spoon on approximately a quarter of the frosting and spread it in a thick layer on top of the cake. Don’t worry about the sides yet.
- Set the 2nd cake on top of the frosting with the flat bottom side of the cake facing up.
- Spoon more frosting on top of the cake in the center and work it out towards the sides. Then begin frosting around the sides of the cake.
- Sprinkle a handful of blueberries on top to garnish as desired.
Equipment
- Stand Mixer Or Hand Mixer and Large Mixing Bowl
- Large Mixing Bowl
- Measuring Cups
- Measuring Spoons
- Fine Mesh Strainer or Sieve For sifting the Almond Flour
- Parchment Paper
- Nonstick Cooking Spray
- Cake Round Optional
- Cake Stand Optional
- Cake Saver Optional
Notes
- Total Carbs per Serving (16 servings) = 30 grams
- Minus Sugar Alcohol per Serving = 21.75 grams
- Minus Dietary Fiber per Serving = 2 grams
- Net Carbs per Serving = 6.25 grams
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