Heat oven to 350°F. Grease a 9x13-inch baking dish.
Spread the cherry pie filling evenly over the bottom of the dish.
Spoon the crushed pineapple with its juices over the cherries and smooth into an even layer.
Dust the fruit with ground cinnamon if using.
Sprinkle the dry cake mix evenly over the fruit. Do not stir.
Drizzle the melted butter across the surface, covering as much of the mix as possible.
Scatter chopped pecans and coconut on top, if desired.
Bake 40–50 minutes until the topping is golden and the edges are bubbly.
Cool 10–15 minutes before serving. Enjoy warm, optionally with vanilla ice cream.