Place 1/2 cup (1 stick) butter in a 13x9-inch baking dish and place in the oven about 3-5 minutes or until butter has melted.
When butter has melted, remove pan from the oven. Stir in rum, then frozen pineapple (don't worry if butter starts to freeze a little when in contact with the pineapple; just make sure everything is well mixed).
Spoon the dry cake mix from the box evenly over pineapple. Sprinkle coconut on top.
Cut remaining 1/2 cup (1 stick) of butter into small cubes and place cubes of butter over cake mix.
Bake dump cake for 45-60 minutes in the middle of the oven or until cooked through and coconut is toasted. Check cake every now and then to make sure coconut does not burn. if coconut starts to get too toasted, cover with aluminum foil.
Dessert will firm up more as it cools. Serve warm or cold. Refrigerate leftovers or until ready to serve. Top with desired toppings as desired.
SNAPPY TIPS: The dessert may look a little soft when removed from the oven. It will harden a bit as it cools. Be sure to check the cake in the oven occasionally to make sure coconut does not burn.SNAPPY SUBSTITUTIONS: Instead of frozen pineapple you can substitute canned pineapple (drained) or fresh pineapple. Instead of rum you can substitute pineapple juice.
Keywords: easy dump cake recipe, pineapple and coconut dessert