Heat oven to 350°F (325°F for dark or nonstick pan). Grease or spray bottom only of 13x9-inch pan.
In large bowl, beat cake mix, water, butter and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes. Pour into pan.
Bake 31 to 36 minutes or until toothpick inserted in center comes out clean. Cool 15 minutes. Poke top of warm cake every 1/2 inch with handle of wooden spoon, wiping handle occasionally to reduce sticking. Reserve 1/2 cup caramel topping. Drizzle remaining caramel topping evenly over top of cake; let stand about 15 minutes or until caramel topping has been absorbed into cake. Run knife around side of pan to loosen cake. Cover and refrigerate about 2 hours or until chilled.
Set aside 2 tablespoons of the reserved 1/2 cup caramel topping. Stir remaining topping into frosting; spread over top of cake. Drizzle with reserved 2 tablespoons caramel topping. Store covered in refrigerator.