Heat the oven to 350°F and butter a 2-quart baking dish with 1 teaspoon of the melted butter.
Toss the drained pineapple with the sugar and flour until no dry streaks remain.
Spread the pineapple mixture in the dish and cover it evenly with the cheddar.
Mix the cracker crumbs with the remaining melted butter until coated.
Scatter the buttered crumbs over the cheese without pressing them down.
Bake for 30 to 35 minutes, until the edges bubble and the cracker top is deep golden, then rest for 10 minutes.