Preheat oven to 350 degrees F. In a 13x9 ungreased pan, pour the crushed pineapple and cherry pie filling in the bottom of the pan. Do not mix, just spread till evenly distributed. Sprinkle the cake mix over the top of the fruit mix.
In a small sauce pan melt the butter over low heat, so as not to burn it. Once the butter is melted, pour over the cake mix in even lines trying to cover as much of the cake mix as possible.
Bake for 50 - 55 minutes, checking after 45 minutes to make sure that it is not over cooking. Cake is done when golden brown. Serve warm or cold.