This beautiful cake is an ode to spring, with piped buttercream icing showing the loveliness of a cherry tree coming into bloom.
Trim the top of the cake with a long serrated knife to make the surface level. Using a ruler as a guide, insert toothpicks or wooden skewers into the sides of the cake at 2-inch intervals to mark two equal layers. Rest the serrated knife on the toothpicks, and halve the cake horizontally using a sawing motion. Carefully slide the top cake layer onto a cardboard round, and set it aside.
With a small offset spatula, spread top of bottom cake layer with 1 1/4 cups frosting; carefully slide the second cake layer back on top of the first cake layer.
Gently brush away loose crumbs from top and sides of cake with a pastry brush. With the offset spatula, spread about 1 1/2 cups frosting over top and sides of cake to form a crumb coat. Refrigerate cake until frosting is firm, about 15 minutes.
With a large offset spatula, spread about 2 more cups frosting over top and sides to form a second coat. Smooth top and remove excess frosting with the large offset spatula. Smooth sides with a bench scraper. Return cake to refrigerator, and chill until second coat is firm, about 15 minutes.
Tint 1 1/2 cups frosting pale pink (for flowers and buds). Tint 1/2 cup frosting a darker pink (for more flowers and buds). Tint 1/2 cup chocolate brown (for branches), and 1/2 cup green (for leaves). Tint 1/4 cup yellow (for dots). Set aside.
Using a toothpick or wooden skewer, mark a pattern on the frosting to serve as a guideline for piping branches.
Decorate cake: Pipe thin branches using brown frosting and a #2 tip. With pink frosting and the #102 petal tip, make basic petals: Hold the bag at a 45 degree angle to the cake, with the tip's wide end down and narrow end pointed away and slightly to the left. Move the tip forward 1/8 inch and back again while you pivot the narrow end to the right. Make five or six petals, turning the cake as you go. Switch to yellow frosting and the #2 tip to pipe dots in the bloom's center. With pink frosting and the #102 petal tip, pipe two small overlapping petals on the branch for a closed blossom. With green frosting and the #3 round tip, pipe a dot, pulling upward, to make a bud; connect to branch with brown frosting. With the #349 tip, pipe tiny green leaves.
Refrigerate cake until ready to serve. Let stand at room temperature 20 minutes before serving. Slice into wedges: To avoid crumbs on surface, make each cut with one downward motion, pulling knife back toward you (not upward) and wiping knife clean after each cut.
Cake can be refrigerated for up to four hours.