Preheat oven to 350 degrees. Grease and flour a 13 x 9 x 2" rectangular baking pan. Beat all ingredients except Caramel Fluff in a large bowl on low speed for 30 seconds, scraping bowl constantly. Neat on high speed for 3 minutes, scraping bowl occasionally. Pour into pan. Bake until a wooden pick inserted in center comes out clean, about 40 to 45 minutes; cool completely. Frost with Caramel Fluff. Store in refrigerator.