To make the sauce, in a large saute pan or soup pot, add the crushed tomatoes, onion and butter. Cover and bring to a simmer.
In the meantime, prepare the meatballs. In a large bowl, mix together all of the meatball ingredients thoroughly. Use a melon baller and your hands to form meatballs.
Once the sauce comes to a simmer, turn the heat to low and add in the meatballs. Cover and cook for 20 minutes. Taste the sauce and season with salt and pepper. Discard the half-onion. Serve the sauce sauce over the pasta, sprinkle with parmesan cheese and serve immediately.