Preheat oven to 350°F and grease and flour two 9 inch round cake pans.
Whisk together flour, baking powder, and salt in a bowl and set aside.
Beat butter and sugar until light and fluffy, about 3 minutes.
Add eggs one at a time, then mix in vanilla.
Alternate adding dry ingredients and milk, mixing just until combined.
Gently fold in rainbow sprinkles.
Divide batter between pans and bake for 25 to 30 minutes until set.
Cool cakes in pans briefly, then transfer to racks to cool completely.
Beat butter, powdered sugar, vanilla, and cream to make the frosting.
Frost the cooled cakes and finish with extra sprinkles.