1 Preheat the oven to 375 degrees F. 2 Mix together mushroom soup, skim milk, parsley flakes, and black pepper in a skillet. 3 Then stir in the cheddar cheese and cook over medium heat until cheese melts, stirring often. 4 Stir in the macaroni, tuna, and pimiento before spreading the mixture into an 8 X 8 inch baking dish sprayed with cooking spray. 5 Bake for 20 to 25 minutes. 6 Remove from oven and let set for 5 minutes before dividing into 4 equal servings.