1/4 c. butter
1/2 c. packed brown sugar
1 can (20 oz.) crushed pineapple, drained
1 pkg. Betty Crocker supermoist carrot cake mix

Heat oven to 350 degrees. Heat butter in rectangular pan, 13 x 9 x 2 inches in oven until melted. Sprinkle with brown sugar. Spoon pineapple over brown sugar; spread evenly. Prepare cake mix as directed on package. Pour over pineapple. Bake 35-40 minutes. Cool 10 minutes. Invert onto heatproof serving platter; remove pan. Cool completely. Top pieces with Cool Whip if desired.