Keto Poppy Seed Lemon Cake with Blackberry Buttercream

You ever had a cake so good it made you stop mid-bite just to appreciate life? That’s this one. A moist, lemony cake with tiny pops of crunch from the poppy seeds, all covered in a smooth, slightly tart blackberry buttercream. And the best part? It’s keto-friendly.

Now, if you’re thinking, “Keto cake? That’s probably dry and tastes like cardboard,” trust me—this is not that. This cake is fluffy, buttery, and bursting with fresh flavors. I’m going to walk you through every step like we’re in the kitchen together, so grab your apron, and let’s make something amazing.

What You’ll Need

Before we get into the magic, let’s talk ingredients. Keto baking is a little different from regular baking, but I’ll explain everything so it makes sense.

For the Cake:

• 2 ½ cups almond flour (this gives a soft texture and keeps it low-carb)
• ¼ cup coconut flour (helps with structure and absorbs moisture)
• 2 tsp baking powder
• ½ tsp baking soda
• ¼ tsp salt
• 3 tbsp poppy seeds (adds that classic crunch)
• 4 large eggs (room temperature for better mixing)
• ¾ cup granulated erythritol or monk fruit sweetener (keeps it sweet without the sugar spike)
• ½ cup unsalted butter, melted
• ⅓ cup sour cream (moisture + richness)
• ¼ cup fresh lemon juice (fresh is best)
• 2 tsp lemon zest (adds extra lemon flavor)
• 1 tsp vanilla extract

For the Blackberry Buttercream:

• 1 cup unsalted butter, softened
• ¾ cup powdered erythritol
• ½ cup fresh blackberries (you can also use frozen, just thaw them first)
• 1 tsp lemon juice (to brighten the flavor)
• 1 tsp vanilla extract

Step 1: Prep Your Ingredients

Start by preheating your oven to 325°F (163°C). Keto cakes bake better at a slightly lower temperature, so they don’t brown too fast before the inside is cooked.

Line two 8-inch cake pans with parchment paper and lightly grease the sides with butter or non-stick spray. This helps the cakes come out easily.

Step 2: Mix the Dry Ingredients

In a large bowl, whisk together the almond flour, coconut flour, baking powder, baking soda, salt, and poppy seeds. Almond flour tends to clump a little, so make sure everything is mixed well.

Poppy seeds are tiny, but they make a difference—little bursts of texture in every bite.

Step 3: Mix the Wet Ingredients

In another bowl, whisk together the eggs and sweetener until it looks pale and slightly fluffy. This step helps the cake have a lighter texture.

Now, add in the melted butter, sour cream, lemon juice, lemon zest, and vanilla extract. Stir until smooth.

At this point, your kitchen should already start smelling like fresh lemons.

Step 4: Combine the Wet and Dry Mixtures

Slowly add the dry ingredients to the wet mixture, stirring gently. You don’t need an electric mixer for this—just a spatula or whisk.

Once everything is mixed, let the batter sit for about 5 minutes. Coconut flour soaks up liquid, and this little rest time helps the batter thicken.

Step 5: Bake the Cakes

Divide the batter evenly between your two prepared cake pans. Smooth the tops with a spatula so they bake evenly.

Bake for 25-30 minutes or until the tops are lightly golden and a toothpick inserted in the center comes out clean.

Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack. Keto cakes are delicate when warm, so handle them gently.

Step 6: Make the Blackberry Buttercream

While the cakes are cooling, let’s make the frosting.

First, blend the blackberries in a food processor or mash them with a fork. If you don’t want seeds in your frosting, strain the puree through a fine-mesh sieve.

Now, in a mixing bowl, beat the butter until creamy. Add the powdered erythritol, blackberry puree, lemon juice, and vanilla extract. Beat until smooth. If it looks too thin, chill it in the fridge for 10-15 minutes before using.

Step 7: Assemble the Cake

Once the cakes are completely cool, place one layer on a plate or cake stand.

Spread a generous amount of frosting on top, then place the second layer over it. Cover the entire cake with the remaining buttercream, smoothing it with a spatula.

For an extra touch, you can press a few fresh blackberries on top.

Step 8: Slice and Enjoy

The hardest part? Waiting. Let the cake chill in the fridge for about 30 minutes before slicing. This helps the flavors blend and makes it easier to cut.

Then, grab a plate, slice yourself a big piece, and taste the magic. A soft, lemony cake with that rich, fruity frosting—it’s everything a dessert should be.

Conclusion

Baking keto cakes takes a little practice, but once you get the hang of it, there’s no going back. This poppy seed lemon cake is proof that low-carb desserts can be just as soft, sweet, and satisfying as traditional ones.

So whether you’re making this for a birthday, a weekend treat, or just because—enjoy every bite. You made something special.

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