Preheat the oven to 350 degrees F (175 degrees C). Grease an 8x8-inch cake pan.

Combine butter and sucralose in a mixing bowl; beat with an electric mixer until creamy. Add egg yolks and vanilla extract and mix well. Add in baking powder and salt.

Mix almond flour and coconut flour into the creamed butter mixture. Pour in heavy cream and mix until combined. Pour batter into the prepared pan.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 20 to 25 minutes.