Preheat the oven to 350°F (175°C) and grease a 9-by-13-inch glass baking dish.
Boil the macaroni in salted water until 1 to 2 minutes shy of al dente. Drain well.
Brown the ground beef in a large skillet over medium heat, breaking it into small pieces. Spoon off excess grease.
Stir the undiluted condensed tomato soup into the beef until evenly combined.
Mix the drained pasta with the beef mixture and 2 cups of shredded cheddar.
Spread the mixture evenly in the prepared baking dish.
Scatter the remaining 1 cup of cheddar over the surface and cover tightly with foil.
Bake for 20 minutes. Remove the foil and bake for another 10 to 15 minutes until bubbling and lightly browned.
Let the casserole rest for 10 minutes before serving.
