Ingredients
  • 4 tablespoons butter
  • 1/3 cup vegetable oil
  • 1 1/4 cups granulated sugar
  • 3 lightly packed tablespoons brown sugar
  • 3 eggs
  • 1/2 cup buttermilk
  • 1/3 cup grapeseed oil
  • 2 teaspoons clear vanilla extract
  • 2 cups cake flour
  • 1 1/2 teaspoons baking powder
  • 3/4 teaspoon kosher salt
  • 1/3 cup rainbow sprinkles, divided
Preparation

Set oven to 350°F.

Combine butter, oil and sugars in a bowl of a stand mixer fitted with the paddle attachment and cream together on medium-high for 2-3 minutes. Scrape down the sides of the bowl, add the eggs and mix on medium-high for 2-3 minutes. Scrape down the sides of the bowl once more.

On low speed, stream in the buttermilk, grapeseed oil and vanilla. Increase the mixer speed to medium-high and paddle for 4-6 minutes, until the mixture is practically white, twice the size of your original fluffy butter-and-sugar mixture, and completely homogenous. Don’t rush; there should be no streaks of fat or liquid. Stop mixer and scrape sides.

On very low speed, add the cake flour, baking powder, salt and 1/4 cup rainbow sprinkles. Mix for 45-60 seconds, until batter comes together. Scrape the sides.

Spray a quarter sheet pan and line it with parchment, or just line the pan with a Silpat. Using a spatula, spread the cake batter in an even layer in the pan. Sprinkle the remaining 2 tablespoons of rainbow sprinkles over the top.

Bake the cake for 30-35 minutes. It will double in size, but remain buttery and dense. At 30 minutes, gently poke the edge of the cake with your finger: the cake should bounce back slightly and the center should no longer be jiggly. Leave the cake in the oven for 3-5 minutes more if it doesn’t pass these tests.

Take the cake out of the oven and cool on a wire rack or, in a pinch, in the fridge or freezer. The cooled cake can be stored in the fridge, wrapped in plastic, for up to 5 days.