Bake 2 round cakes according to the cake mix box instructions. Allow the cakes to cool in the pan for a few minutes before transferring to a cooling rack.
Cool the cake completely, then cut each cake according to the diagram using a serrated knife.
Beat butter with an electric mixer for two minutes. Add sifted powdered sugar and mix until creamed.
Beat in heavy whipping cream and vanilla. Scrape sides of the frosting bowl with a rubber spatula.
Place the cut cake pieces on a foil-covered platter or cutting board. Spread buttercream frosting, with a spatula or butter knife, along the bottom of the bunny face cake to attach the bow tie. Spread frosting on the bottom of each ear to attach the ears to the bunny's head.
Cover the entire cake in the frosting.
Decorate the cake with candy, coconut, jelly beans, or any type of spring candy you'd like.
Notes
You will have extra frosting leftover. Store the frosting in the freezer for up to 6 months to use in another recipe!