Heat a large skillet over medium-high heat. Add the ground beef, breaking it apart as it cooks for about 3 minutes. Once browned, stir in the chopped onions and continue cooking until the meat is no longer pink, roughly 6 more minutes. Drain any excess grease.

While the beef is cooking, bring a large pot of water to a boil with 1/2 tablespoon of salt. Add the macaroni and cook until al dente, about 7-9 minutes. Drain the pasta, reserving some water if needed.

In the same skillet, melt 2 tablespoons of butter over medium heat. Stir in the minced garlic; cook for about 1 minute until fragrant. Add flour and tomato paste, mixing well. Cook for 1-2 minutes.

Gradually pour the sauce mixture into the skillet with the beef, stirring constantly to prevent lumps. Cook until it comes to a gentle boil, about 3-5 minutes. Reduce heat to low and simmer for another 5 minutes.

Stir in the drained macaroni and shredded cheddar cheese until fully melted. For extra gooeyness, add more cheese on top and cover for a few minutes. Serve hot.