finely grated lemon and lime peels, if desired1 Heat oven to 350°F. Spray bottom only of 13x9-inch pan with cooking spray.
large bowl, beat Cake Layer ingredients with electric mixer on medium speed 2 minutes, scraping bowl occasionally. Pour in pan.
another large bowl, mix Lemon-Lime Layer ingredients with whisk until smooth. Evenly pour over top of cake batter in pan; mixture will sink to bottom as you pour over cake batter.
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.
Some days ago, this magiccake took us by storm. Truly, it was magical. If you're anything like me, the best part of this cake is watching it poof up in the oven into an amazing dome then sink back into the original flat shape later