1½ cups coarsely crushed pretzels
½ cup sugar
½ cup butter or margarine, melted
1 box white cake mix
1¼ 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
Grated lime peel or wedges, if desired
Heat oven to 350°F for shiny metal or glass pan (or 325°F for dark or nonstick pan). Spray bottom only of 13x9-inch pan with baking spray with flour. In medium bowl, mix pretzels, sugar and butter. Sprinkle evenly on bottom of pan; press gently.
In large bowl, beat cake mix, margarita mix, oil, lime peel and 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 1 hour. Frost with whipped topping; sprinkle with lime peel. Store covered in refrigerator.