You want to turn all your cake into Funfetti cake, don't you?
1. Begin with any ol' yellow cake batter. You can use a cake mix or your favorite recipe. Or, if you want to make sure it's the *best* yellow cake, use THIS ONE.
2. Then buy yourself some SPRINKLES.
3. Then just fold the sprinkles into the cake batter and bake as usual.
For a standard box of cake mix, or any recipe that makes a two- or three-layer cake, combine 1/2 cup sprinkles with 1 Tbsp. flour. (The flour will coat the sprinkles so that the sprinkles float in your batter, rather than sink to the bottom.)