Bake 30 to 35 minutes or until toothpick inserted in center comes out clean. Cool 30 minutes. Refrigerate at least 4 hours to chill. Spread whipped topping over chilled cake. Sprinkle with additional lemon and lime peel if desired. Using a serving spatula and a knife to carefully help slide pieces off, cut into 6 rows by 3 rows. Store covered in refrigerator.