Sprinkle the buttered cracker crumbs evenly over the pineapple mixture, covering the surface from corner to corner. Scatter the remaining 1/2 cup of shredded sharp cheddar cheese over the cracker layer so it melts into the crust as it bakes.
Place the dish on the middle rack of the preheated oven and bake for 25–30 minutes, or until the top is golden brown, the cheese is melted, and you can see the pineapple filling bubbling gently around the edges.
Remove from the oven and let the casserole rest for about 10–15 minutes before serving. This short rest helps the juices settle so each scoop holds together while still warm and gooey.
Serve warm, scooping down through the melted cheddar and buttery cracker crust to get plenty of pineapple in every serving. Store any leftovers covered in the refrigerator and reheat gently in the oven to re-crisp the topping.
If your family prefers a little less sweetness, you can cut the sugar down to 3/4 cup or even 1/2 cup, especially if your pineapple is very ripe. For a slightly different texture, use pineapple tidbits instead of chunks, or mix the two—chunks give those big, juicy bites that feel most like the old church potlucks. Extra-sharp or aged cheddar brings more tang and keeps the casserole from tasting like straight dessert; avoid mild cheddar, which can get lost in the sweetness. If you only have pineapple in syrup, drain it very well and reduce the sugar by at least half. For a sturdier topping, crush some of the crackers finely and leave a few a bit chunkier so you get a mix of crisp and buttery bites. You can assemble the casserole a few hours ahead, keep it covered in the refrigerator, and add the cracker-cheese topping just before baking so it stays crisp. Leftovers reheat best in the oven, uncovered, at 325°F until warmed through and the top has regained some crunch.
