To prepare a traditional reuben casserole recipe, you will first need to prepare the ingredients for the casserole. You will need: 1 pound ground beef 2 tbsp. ketchup 1 cup mayonnaise 1/2 cup chopped scallions 1 teaspoon kosher salt 2 tablespoons butter 1 tablespoon melted margarine 2 cups shredded cheddar cheese 1 1/2 teaspoons paprika Instructions: Preheat the oven to 350 degrees F (180 degrees C) and grease an 8 x8-inch baking dish with nonstick cooking spray. Place the beef in the dish and sprinkle with the salt and pepper. Bake for 1 hour and 15 minutes or until the meat is no longer pink and the cheese is bubbling. Remove from oven and let stand for 5 minutes before serving.