Preheat the oven to 350°F (175°C) and grease two 8-inch cake pans.
In a bowl, whisk together the almond flour, coconut flour, baking powder, salt, and sweetener.
In a mixing bowl, beat the softened butter until creamy, then add the eggs one at a time, mixing well after each addition.
Mix in the vanilla extract and almond milk until smooth.
Gradually add the dry ingredients to the wet ingredients, mixing until combined.
Divide the batter evenly between the cake pans and smooth the tops with a spatula.
Bake for 22-25 minutes, or until a toothpick inserted in the center comes out clean.
Let the cakes cool in the pans for 10 minutes before transferring to a wire rack to cool completely.
Frost the cake with keto buttercream frosting and decorate with sugar-free sprinkles if desired.
Chill the cake for 30 minutes before slicing and serving.