Decorate cake. Prepare buttercream icing following recipe directions. Tint portions peach and a light peach. Use spatula and peach icing to ice cake smooth.
Use ruler and toothpick to mark cake sides 2 in. down from top border.
Use tip 104 and light peach icing to pipe ruffle in Cornelli lace-like pattern on top of cake and extending down 2 in. on sides by holding decorating bag at a 90° angle with wide end of tip facing down. Use tip 3 and light peach icing to pipe dots on cake sides. Use tip 12 and peach icing to pipe bead bottom border.