Bring a large pot of lightly salted water to a boil. Cook macaroni according to package directions until tender; drain.

Meanwhile, cook and stir ground beef and onion in a large skillet over medium-high heat until beef is browned and crumbly, about 10 minutes. Drain well. Stir in tomato soup until combined.

Return drained macaroni to the pot. Add beef mixture and stir until well combined. Season with salt and ground black pepper.