In a large mixing bowl, combine the ground beef, finely chopped onion, minced garlic, egg, breadcrumbs, grated Parmesan cheese, dried oregano, and a pinch of salt and pepper. Mix well until all ingredients are fully combined.
Shape the mixture into small meatballs, about 1 inch in diameter.
In a large frying pan, heat a little oil over medium heat. Add the meatballs and cook until they are browned on all sides and cooked through, about 10-12 minutes. Remove the meatballs from the pan and set them aside.
In the same pan, add the canned chopped tomatoes, tomato paste, sugar, and a pinch of salt and pepper. Stir well and bring to a simmer. Let it cook for about 10 minutes, allowing the sauce to thicken.
While the sauce is simmering, cook the spaghetti according to the package instructions until al dente. Drain and set aside.
Once the tomato sauce has thickened, return the cooked meatballs to the pan. Simmer for an additional 5 minutes, allowing the meatballs to soak up some of the sauce.
Serve the spaghetti topped with the meatballs and tomato sauce. Garnish with fresh basil leaves.
