Dump the can of cherry pie filling in the bottom of your baking dish. Next, dump the crushed pineapple on top, mix around with your finger. Just kidding. If you are serving this to guests, use a proper utensil.
Next dump the box of yellow cake mix on top of the fruit mixture. If you like nuts, sprinkle some on top.
Take a stick of butter and slice it all over the top. Bake at 350 for 30-45 minutes, until top is browning.
It's best to let it cool a little before serving. If it's piping hot out of the oven it will ooze all over the place and the fruit filling is hot as hell.
I could literally stand over the stove and eat the topping with a fork. Forget the fruit, I love the buttery crunch of the yellow cake mix on top. Jim and I served this to friends one night and had half a pan left over the next morning. We tossed it. Not because it was bad, but because it is SO good and we didn't need to be standing over the stove eating this dump cake out of the pan with a fork. It's THAT good.