Heat oven to 350 degrees (325 F for dark or nonstick pans). Line 2 (8 inch) round pans with foil, allowing foil to hang 2 inches over 2 opposite sides of pans. Generously spray bottoms and sides of foil with cooking spray.
Make cake mix as directed on box using water, oil and eggs. Pour into pans. Bake 28 to 33 minutes or until toothpick inserted in center of cake comes out clean. Cool 15 minutes.
In a small bowl, mix powdered sugar and lemon juice. Poke top of warm cake every 1/2 inch with long-tined fork, wiping fork occasionally to reduce sticking. Drizzle and spread lemon mixture over top of cake. Refrigerate about 2 hours or until chilled. Remove cakes from pans by lifting with foil; peel away foil.
Microwave frosting uncovered on high 15 seconds. On serving plate place 1 cake, rounded side down; trim if necessary so layer rests flat. Spread with half of frosting. Top with second cake, rounded side up. Frost top of cake with remaining frosting. If desired, garnish with lemon drop candies. Store loosely covered at room temperature.