Keto Banana-Nut Cake with Sugar-Free Buttercream
Soft, moist, warmly spiced, and packed with walnut crunch, this keto-friendly banana-nut cake is a delicious alternative to traditional banana cake. Since real bananas are relatively high in carbohydrates, this version uses a small amount of banana extract for that classic flavor while keeping the cake lower in carbs.
🍰 Servings
10–12 slices
⏱️ Prep Time
15 minutes
🔥 Bake Time
25–30 minutes
⏱️ Total Time
45 minutes
🧾 Cake Ingredients
- 2 cups almond flour
- ¼ cup coconut flour
- ½ cup granulated keto sweetener, such as allulose or erythritol
- 1½ tsp baking powder
- ½ tsp baking soda
- ½ tsp salt
- 1 tsp ground cinnamon
- ¼ tsp nutmeg
- 4 large eggs, room temperature
- ½ cup unsalted butter, melted and slightly cooled
- ½ cup unsweetened sour cream or plain Greek yogurt
- 2 tsp banana extract
- 1 tsp vanilla extract
- ½ cup chopped walnuts
- 2 tbsp unsweetened almond milk, if needed
🧁 Sugar-Free Buttercream
- ½ cup unsalted butter, softened
- 1½ cups powdered keto sweetener
- 1–2 tbsp heavy cream or unsweetened almond milk
- 1 tsp vanilla extract
- ½ tsp banana extract
- Pinch of salt
👩🍳 Instructions
1. Prepare the oven
Preheat your oven to 350°F (175°C).
Grease two 8-inch round cake pans and line the bottoms with parchment paper.
2. Mix the dry ingredients
In a medium bowl, whisk together the almond flour, coconut flour, keto sweetener, baking powder, baking soda, salt, cinnamon, and nutmeg.
Break up any lumps of almond flour.
3. Combine the wet ingredients
In a separate large bowl, whisk the eggs until lightly beaten.
Add the melted butter, sour cream or Greek yogurt, banana extract, and vanilla extract. Whisk until smooth.
4. Make the batter
Gradually add the dry ingredients to the wet mixture.
Stir gently until just combined. Don’t overmix.
Fold in the chopped walnuts.
If the batter seems unusually thick, add 1–2 tablespoons of unsweetened almond milk.
5. Divide and bake
Divide the batter evenly between the prepared cake pans.
Smooth the tops with a spatula.
Bake for approximately 25–30 minutes, or until the center is set and a toothpick inserted into the middle comes out mostly clean.
Don’t overbake—the cake should remain soft and moist.
6. Cool completely
Let the cakes cool in their pans for about 10 minutes, then carefully transfer them to a wire rack.
Allow them to cool completely before frosting.
🧈 Make the Sugar-Free Buttercream
1. Beat the butter
Place softened butter in a mixing bowl and beat for 2–3 minutes until light and fluffy.
2. Add the sweetener
Gradually add the powdered keto sweetener while mixing on low speed.
Once incorporated, increase the speed and beat until smooth.
3. Add flavor
Add vanilla extract, banana extract, and a pinch of salt.
Add heavy cream or almond milk 1 tablespoon at a time until the frosting reaches a smooth, spreadable consistency.
🎂 Assemble the Cake
Place one cooled cake layer on a serving plate.
Spread an even layer of buttercream over the top.
Place the second cake layer on top and gently press down.
Cover the top and sides with the remaining buttercream.
Finish with a sprinkle of chopped walnuts and, if desired, a light dusting of cinnamon.
💡 Keto Tips
- Don’t use regular bananas if you’re specifically keeping the cake keto, as they can substantially increase the carbohydrate content.
- Banana extract provides the familiar banana flavor without adding the carbohydrates from a whole banana.
- Use allulose if you prefer a softer frosting and cake texture; erythritol can sometimes create a slightly cooling sensation.
- Let the cake cool completely before frosting to prevent the buttercream from melting.
- Store covered in the refrigerator for up to 4 days and allow slices to sit at room temperature for a few minutes before serving.
Note: Exact net carbs depend on the brands of almond flour, coconut flour, sweetener, dairy products, and extracts used, so calculate the nutrition from your specific ingredients if you’re tracking carbs closely.
