I found this recipe on another blog and I don't want to lose it so I am posting it here.
1 box yellow cake mix
1 1/4 cups bottled nonalcoholic margarita mix
1/3 cup vegetable oil
1 tablespoon grated lime peel
3 egg whites
1 container (8 oz) frozen whipped topping, thawed or homemade butter cream frosting with lime juice added
Additional grated lime peel, if desired
1. Heat oven to 350°F (or 325°F for dark or nonstick pan). Grease bottom only of 13x9-inch pan with shortening and lightly flour (or spray bottom with baking spray with flour).
2. In large bowl, beat cake mix, margarita mix, oil, 1 tablespoon lime peel and the egg whites with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl occasionally.
3. Bake 35 to 40 minutes or until light golden brown and top springs back when touched lightly in center. Cool completely, about 2 hours. Frost with whipped topping or icing; sprinkle with additional lime peel. Store covered in refrigerator.