The classic cocktail, now in (optionally) non-alcoholic dessert form!
Turn the oven up to 350 F. While that's heating up, grease and flour a 9x13-inch cake pan.
In a big mixing bowl, beat the cake mix, egg whites, frozen margarita mix, vegetable oil, lime zest, and 1 tablespoon lime juice together. Pour the newly created batter into the pan you prepped.
Bake the pan in the preheated oven until you can stick a toothpick in and see moist crumbs, 30 to 35 minutes. Don't worry, it's supposed to be really moist. Let the cake cool in the pan.
Now for the frosting. Beat the cream cheese and butter together until it's light and fluffy, then stir in the lemon peel and 1 tablespoon of lime juice. Beat in the confectioners' sugar, 1 cup at a time. Make sure to scrape the sides of the bowl thoroughly with a spatula after each addition. Spread the frosting over the cooled cake.
If you want to make this recipe a little more adult-oriented, add 3 shots of either rum or tequila to the icing.