Margarita Cake

I tried this recipe for a Mexican fiesta at school this week and it was GREAT! A wonderful, light dessert to eat at the end of a heavy Mexican food meal! The pretzel crust was wonderful to balance out the sweetness of the cake.

1 1/2 cups coarsely crushed pretzels
1/2 cup sugar
1/2 cup butter or margarine, melted
1box white cake mix
1 1/4 cups bottled nonalcoholic margarita mix (at Kroger on the wine aisle)
1/3 cup vegetable oil
1 tablespoon grated lime peel
3egg whites
1 container (8 oz) Cool Whip

Heat oven to 350 degrees. Spray bottom of 13x9-inch pan. In medium bowl, mix pretzels, sugar and butter. Sprinkle evenly on bottom of pan; press down gently. 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. Pour batter over pretzel mixture. 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; sprinkle with additional lime peel. Store covered in refrigerator.