Preheat oven to 350°F. Spray 2 8-inch round baking pans with a nonstick baking spray. Set aside.
In a large bowl, with a hand or stand mixer, cream together the sugar and butter until well combined and fluffy, about 3-5 minutes. Mix in the eggs, one at a time, mixing well between each addition. Mix in the vanilla. Turn the mixer on high and continue mixing until fluffy and creamy, about 2-3 minutes. Set aside.
2 cups granulated sugar, 1 cup unsalted butter, 4 large eggs, 1 tablespoon pure vanilla extract
In a small bowl, sift together the flour, baking powder, baking soda and salt. Turn on the mixture and pour ⅓ of the flour mixture into the batter, mix well. Add ⅓ of the milk into the batter, mix well. Keep alternating between the flour and milk until all is mixed in continue mixing for another 2-3 minutes. Gently fold in the sprinkles. The batter will be creamy smooth.
3 cups all-purpose flour, 3 teaspoons baking powder, 1 teaspoon baking soda, ½ teaspoon kosher salt, 1¼ cups milk, ¾ cup rainbow sprinkles
Bake for 35-40 minutes. Until a toothpick is inserted in the center and comes out clean.
Cool for 10 minutes before inverting the pan and removing the cake to a cooling rack. Cool completely before frosting.