1 1/2 cups coarsely crushed pretzels
1/2 cup sugar
1/2 cup butter or margarine, melted
1 box Betty Crocker® SuperMoist® white 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
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). In medium bowl, mix pretzels, sugar and butter. Sprinkle evenly on bottom of pan; press gently.
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. Pour batter over pretzel mixture.
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; sprinkle with additional lime peel.
Store covered in refrigerator.
High Altitude (3500-6500 ft): Heat oven to 375°F. Decrease oil to 1/4 cup; use 4 egg whites.