Preheat oven to 350F
Spray a 6 inch cake pan with non stick cooking spray and line the bottom with a greased piece of parchment paper. Set aside.
In a medium bowl, combine the yellow cake mix, egg, butter and milk. Mix for 2 minutes until very well combined.
Add in the sprinkles and mix gently until spread throughout.
Pour batter into prepared baking pan. Bake for 35-45 minutes or until toothpick inserted in the center comes out clean.
Remove from oven, let it sit in the pan for 10-15 minutes then invert onto a wire rack to fully cool.
If you want a one later cake, simply frost, decorate and enjoy!
If you want a two later cake, slice the cake in half using a Serrated knife. Add an even layer of frosting to one half and top with the other piece of cake. Now frost the whole cake and add sprinkles.