In a large Dutch oven or a deep skillet over medium-high heat, add the ground beef and diced onions. Cook until the beef is fully browned and the onions are soft and translucent. Drain any excess grease from the pan. Add the minced garlic and cook for another 1 minute until fragrant.
Stir in the tomato sauce, diced tomatoes, beef broth, soy sauce, Italian seasoning, salt, and black pepper. Mix everything well to combine. Bring the mixture to a gentle boil, then reduce the heat to low. Cover the pot and let the sauce simmer for about 10 minutes to allow the flavors to develop.
Add the uncooked elbow macaroni directly into the pot with the sauce. Stir well to ensure the noodles are submerged. Cover the pot again and simmer for 10 to 12 minutes, or until the pasta is tender. Stir occasionally to prevent the noodles from sticking to the bottom of the pot.
Once the pasta is cooked, turn off the heat. Stir in the shredded cheddar cheese until it is completely melted and the sauce is creamy. Taste and adjust seasoning if necessary. Garnish with fresh parsley and serve immediately while hot.