Preheat your oven to 350°F and grab a 9x13 inch baking dish—no need to grease it. Open both cans of crushed pineapple and here's the important part: do NOT drain them. Dump both cans with all their juice into the bottom of the dish. Spread the pineapple out evenly so it covers the whole bottom in one layer. That juice is what makes your pineapple dump cake gooey instead of dry, so seriously don't pour it out. If you're making cherry pineapple dump cake, you can dump a can of cherry pie filling on top of the pineapple now.

Open your box of yellow cake mix and dump the entire thing over the pineapple. Don't mix it, don't stir it, don't even think about touching it—just spread the dry mix evenly with a spatula so it covers all the wet fruit. You shouldn't see any pineapple peeking through. Make sure you get it in the corners too. The dry cake mix is going to absorb butter from above and juice from below and turn into this amazing crust. This is why it's called a dump cake—you literally just dump stuff and walk away.

Melt all your butter in the microwave until it's completely liquid—no chunks floating around. Now here's where people mess up: drizzle the melted butter evenly over the ENTIRE surface in thin streams, going back and forth like you're drawing lines. Don't just dump it all in the middle and hope it spreads because it won't. Use a spoon to make sure every bit of dry cake mix gets hit with butter, especially the corners and edges. If you want nuts or coconut, sprinkle them on top now. Every spot that gets butter will bake into golden crust, every spot that doesn't will stay raw powder.

Stick it in your preheated 350°F oven and bake for 55-65 minutes until the top is golden brown and bubbly around the edges. You'll know it's done when the whole top looks crispy and you can see the pineapple bubbling up on the sides. Pull it out and—this is important—let it cool for at least 10-15 minutes before you serve it. I know it smells incredible but serve it immediately and you'll burn everyone's mouth plus the filling will be straight liquid. Those 15 minutes let it set up so it's gooey instead of molten lava. Serve warm with vanilla ice cream or whipped cream.