In a large pot, brown the ground beef over medium heat, breaking it apart as it cooks. Drain any excess fat.
Add the diced onion, garlic, and bell pepper. Cook until softened, about 5 minutes.
Stir in the diced tomatoes, tomato sauce, kidney beans, beef broth, chili powder, cumin, salt, and pepper.
Bring to a boil, then reduce heat to simmer for 15 minutes.
Add the elbow macaroni and cook for an additional 10-12 minutes, or until the pasta is tender.
Serve hot, garnished with shredded cheese and green onions.