In a large pot, heat olive oil over medium heat. Add chopped onion and minced garlic; sauté until softened.
Add ground beef to the pot and cook until browned, breaking it up into small pieces.
Stir in crushed tomatoes, tomato paste, Italian seasoning, salt, and black pepper.
Add water and bring the mixture to a simmer.
Break spaghetti pasta in half and add to the simmering sauce, stirring to submerge the pasta.
Cover and simmer gently, stirring occasionally, until pasta is soft and meatballs are cooked through, about 20 minutes.
Stir in grated parmesan cheese just before serving.
Serve in shallow white bowls with meatballs evenly distributed and sauce coating the pasta.