Preheat your oven to 350°F (175°C). A hot oven means a bubbly casserole, and we want that!

Grab a medium-sized casserole dish and grease it with a little butter or cooking spray. This will prevent sticking.

In a medium saucepan, melt the butter over medium heat. Whisk in flour until smooth. Slowly add the reserved pineapple juice while continuing to whisk. Once combined, sprinkle in the cheese and stir until melted and creamy. This is where the magic starts!

In a large mixing bowl, combine the drained pineapple tidbits, the cheese mixture, and sugar. Stir until the pineapple is well coated.

In a small bowl, mix the crushed crackers and chopped nuts. This will give your casserole that irresistible crunch.

Spoon the pineapple and cheese mixture into the prepared dish. Evenly spread the cracker and nut topping over the pineapple mixture.

Place the casserole in the preheated oven. Bake for about 30-35 minutes or until the top is golden and bubbly.

Once done, remove it from the oven and let it cool for a few minutes. Serve warm and watch it disappear!