Preheat oven to 350℉ and grease the cake pan generously with butter.
Beat butter until light and fluffy, then add the erythritol and allulose and beat.
Add eggs, one at a time, scraping the bowl down and beating after each addition until well mixed.
Add Keto Chow, almond flour, coconut flour, and baking powder and beat until well combined.
Add the almond milk, sour cream, and extract. Beat well, scraping down the bowl to be sure there are no unincorporated dry ingredients. The batter will be thick.
Spread the batter into the pan and bake on the center rack of the oven for approximately 30-35 minutes, or until the cake is golden and a tester comes out clean and the center springs back when lightly touched. Let cool.
To make the frosting, beat the butter in a large mixing bowl with an electric mixer until light and fluffy.
Add the powdered erythritol and beat well, starting on low speed and then increasing once the erythritol is combined with the butter.
Add the Keto Chow and mix well.
Add the heavy cream and extract and beat until light and fluffy.
When the cake is completely cool, spread the frosting generously over the cake and decorate with sprinkles.
Notes
The allulose in the cake helps keep the cake tender but it also creates a very brown crust. It can be replaced with an equal amount of erythritol.