Birthday Confetti Cake

Ingredients

• 3 cups all-purpose flour
• 3 teaspoons baking powder
• 1/2 teaspoon kosher salt
• 1 cup (2 sticks) unsalted butter, softened
• 2 cups granulated sugar
• 5 large eggs
• 1 tablespoon pure vanilla
• 1 and 1/2 cups whole milk or buttermilk
• 1 cup rainbow sprinkles
• 1/2 cup (1 stick) unsalted butter, softened
• 4 ounces cream cheese, softened
• 1/4 teaspoon kosher salt
• 1 teaspoon pure vanilla
• 4 cups powdered sugar
• 1-2 tablespoons milk
• 1/3 cup rainbow sprinkles, for garnishing the top of the cake