1 pkg. Duncan Hines yellow cake mix
1 med. can crushed pineapple
1 can blueberry pie filling
1 stick butter

Use 9 x 13 pan. Put the blueberry pie mix in the bottom of the pan, then add the pineapple. Mix cake according to directions; pour over the top. Add the stick of butter cut up over the top.

Bake at 350 degrees as cake calls for. Let stand 15-20 minutes; cool. Frost with Cool Whip.