Preheat the oven to 350°F. Grease a 1 cup (8oz) ramekin or oven safe bowl with nonstick spray. Whisk the cake batter: In a small mixing bowl, mix together the cake mix, protein powder, egg, milk, and coconut oil until smooth. Transfer to the greased ramekin. It should be filled almost all the way to the top (you want it to bake taller than the edges).
5 Tablespoons Simple Mills Cake Mix, 2 Tablespoons vanilla protein powder, 1 egg, 2 tablespoons milk, 1 tablespoon coconut oil
Bake the cake: Bake in the preheated oven for 20-22 minutes, until a toothpick insert in the center comes out with a few moist crumbs. Remove and let it cool completely. You can put it in the fridge or freezer to speed it up. If you used the correct size baking dish it should bake up perfectly level with the top of the glass. You can cut off some of the top so it’s flat.
Frost the cake: Mix the prepared frosting and protein powder in a small dish until smooth. Use a knife or offset spatula to frost the cake in an even layer so it's level with the top of the baking dish.
2 Tablespoons vanilla cake frosting, 2 teaspoons vanilla protein powder
Dip into sprinkles: Pour the rainbow sprinkles on a plate. Turn the frosted cake upside down into the sprinkles, gently pushing the edges in so the sprinkles cover the entire cake. Lift the cake and double check it's completely coated. Press back down into bare areas if needed. Enjoy right away or refrigerate overnight before eating.
Nonpereil rainbow sprinkles