Whisk butter, sugar, eggs, milk, and vanilla until smooth.
Fold in flour, baking powder, baking soda, and salt. Do not overmix.
Divide batter into 3 silicone pans. Microwave each layer for 3 min 15 sec.
Cool completely before frosting.
Beat butter until smooth, add sugar, milk, vanilla. Whip until fluffy.
Assemble layers with frosting, cover cake with remaining frosting.
Decorate with sprinkles.
