Preheat oven to 350F degrees. Spray two 8 or 9-inch round springform or baking pans generously with nonstick spray. Set aside.

In a medium bowl, mix together flour, baking powder, baking soda, and salt. Set aside. In a large microwave-safe bowl, melt butter in the microwave. Whisk in the sugars vigorously getting out any lumps. Whisk in the egg, yogurt, milk, and vanilla extract until combined. Slowly mix in dry ingredients until no lumps remain. The batter will be thick. Slowly stir in the sprinkles, but do not overmix because the sprinkles will bleed their color.

Pour the batter into the prepared cake pan. This cake takes around 33-37 minutes to bake. Start checking the cake after 33 minutes, and keep baking until a toothpick inserted in the center comes out clean. Allow to cool.

Cream the room temperature butter with an electric mixer, until smooth and fluffy. Gradually beat in confectioners' sugar until fully incorporated. Start with less and add in more to get the desired consistency. Beat in the vanilla extract.

Pour in the milk (start with 1 or 2 tablespoons, then add more if needed) and beat for an additional 3-4 minutes. Add food coloring, if using, and beat for thirty seconds until smooth or until desired color is reached.

Invert one of the cakes on a cake pan, and spread about 1/2 cup of frosting on top. Invert the other cake on top, and spread the rest of the frosting on the top and sides of the cake. Smooth out the tops and sides with a cake spatula. Decorate the cake with a piping bag and add more sprinkles if desired.