In a large Dutch oven, cook and stir the ground beef over medium-high heat, breaking the meat up as it cooks, until the meat is no longer pink and has started to brown, about 10 minutes. Skim off excess fat, and stir in the onions and garlic. Cook and stir the meat mixture until the onions are translucent, about 10 more minutes.
Stir in water, diced tomatoes, and bring the mixture to a boil over medium heat. Reduce the heat to low, cover, and simmer 20 minutes, stirring occasionally
Stir in the macaroni with salt, cover, and simmer over low heat until the pasta is tender, about 25 minutes, stirring occasionally. Remove from heat and top with grated parmesan cheese, and serve.