Step 1: Preheat your oven to 350°F (175°C).
Step 2: Grease and flour your 9-inch round cake pans.
Step 3: In a large mixing bowl, whisk together the all-purpose flour, baking powder, and salt until well combined. Set aside.
Step 4: In another bowl, combine the melted unsalted butter and granulated sugar. Beat until blended, then add eggs one at a time, mixing well after each. Stir in vanilla extract and buttermilk.
Step 5: Gradually add the dry ingredients to the wet mixture, mixing until just combined. Gently fold in the rainbow sprinkles.
Step 6: Divide the batter evenly between the prepared pans and bake for 25-30 minutes, or until a toothpick comes out clean.
Step 7: Let the cakes cool in the pans for about 10 minutes, then transfer to a cooling rack to cool completely.
Step 8: To make the frosting, beat softened butter until creamy, then gradually add powdered sugar. Mix in vanilla extract, salt, and cream until fluffy.
Step 9: Once the cakes are cool, place one layer on a serving plate, spread frosting on top, then add the second layer and frost the sides and top.
Step 10: Top with additional rainbow sprinkles!
