Preheat your oven to 350°F (175°C).
Pour both cans of crushed pineapple, including all the juice, into the bottom of the 9×13 inch baking dish. Spread the fruit into an even layer using a spatula.
Sprinkle the dry yellow cake mix evenly over the pineapple layer. Do not stir the mixture; simply ensure the fruit is completely covered by the powder.
Distribute the shredded coconut across the top of the cake mix layer.
Place the thin pats of butter across the entire surface of the cake mix. Try to cover as much of the surface as possible to ensure the cake mix hydrates properly during the bake.
If using nuts, sprinkle them over the top at this stage.
Bake for 30 to 35 minutes. The dessert is finished when the edges are bubbling vigorously and the top has turned a light golden brown.
Remove from the oven and let it cool for at least 10 minutes before serving, as the pineapple filling will be extremely hot.