Pink Lemonade Cake

1 package (1 lb, 2.25 oz) white cake, preferably Duncan Hines
2 egg whites
1 egg
2 tablespoons oil
3 tablespoons grated lemon zest -- divided
1/2 cup maraschino cherries (drained & coarsely chopped)
1/4 cup sugar
1/4 cup lemon juice
2 cans (16 oz each) vanilla frosting
Red food coloring -- optional
Maraschino cherries with stems -- optional

Preheat oven to 350ºF. Butter and flour 2 (8") round cake pans. In bowl at low speed beat cake mix, egg whites, egg, 1 1/3 cups water, oil and 1 tbsp zest until moistened, about 30 seconds. Increase speed to medium; beat 2 minutes. Divide batter between pans. Sprinkle top of batter in each pan with 1/4 cup cherries. Bake 32-35 minutes or until toothpick inserted into centers comes out clean. In pot combine 2/3 cup water with sugar and lemon juice. Over high heat bring mixture to boil; cook until syrupy, 7-9 minutes. Remove syrup from heat; reserve. Cool cake layers in pans on racks 20 minutes; remove from pans. Return to racks set over paper towels. Using toothpick gently poke holes in cake tops. Brush lemon syrup over tops; cool completely. In bowl stir remaining zest into frosting; if desired, stir in food coloring to tint pink. Place 1 cake layer on serving plate; spread with 1 cup frosting. Top with remaining cake layer. Spread top and side of cake with remaining frosting. Garnish with cherries, if desired.