Sprinkles: Use bright ones! I have found that naturally-dyed sprinkles can lose their color when baked. 

Funfetti Cake

Serves: 10 to 14

Ingredients

Cake

• 1cup (2 sticks) unsalted butter, at room temperature
• 1 1/2cups sugar
• 4large egg whites
• 2tablespoons clear imitation vanilla (I use McCormick's --see headnote)
• 6tablespoons vegetable oil
• 2 1/2cups cake flour (see headnote)
• 2 1/4teaspoons baking powder
• 3/4teaspoon salt
• 1cup whole milk
• 2/3cup plus 1 tablespoon sprinkles (see headnote)

Frosting

• 2cups (or 4 sticks) unsalted butter, at room temperature
• 3cups powdered sugar, or to taste
• 2teaspoons clear imitation vanilla
• 1pinch salt

Directions

Cake

1. Preheat oven to 350° F. Grease two 8-inch cake pans. Cut out circles of parchment paper and line the bottom of the pans. Lightly spray the parchment.
2. With an electric mixer or in the bowl of a stand mixer, cream together the butter and sugar until fluffy. Add the egg whites, one at a time, mixing well after each one. Mix in the vanilla and oil.
3. In a medium bowl, whisk together the flour, baking powder, and salt. With your mixer running on low, add this to the butter mixture in three additions, alternating with the milk. Once you have a smooth batter, fold in the 2/3 cup of sprinkles.
4. Divide the batter evenly between the pans. Sprinkle the remaining tablespoon of sprinkles over the top and bake the cakes until a toothpick inserted into the center comes out clean. Begin checking for doneness at around 25 minutes.
5. Let the cakes cool for a few minutes in the pans and then flip them onto a cooling rack to cool completely before frosting.
6. To make the colorful bunting, knead food coloring (liquid or gel) into marzipan, cut out triangles, and stick them onto the cake.

Frosting

1. Beat together the butter and sugar until creamy. Add the vanilla and salt and mix to combine. Taste and add more sugar, if desired.
2. Frost your cake and enjoy!

https://food52.com/recipes/30792-funfetti-cake