To prepare a apple tuna pasta casserole main dish recipe, you will first need to prepare the ingredients for the casserole. Peel and slice an apple and cut it into quarters. Place the quartered apples in the bottom of an 8 x8-inch baking dish. Pour the melted butter over the top of the apple slices. Sprinkle the chopped scallions, thyme, and salt and pepper on top. Bake the dish at 350? for 45 to 50 minutes or until the apples are tender and the topping is lightly browned.