Directions

1. Combine tomatoes, butter and onion in a medium pot over medium-high. Bring to a light boil, then turn heat down to medium-low so the sauce is simmering. 
2. Let cook, uncovered, for 40-45 minutes, until you see droplets of butterfat rise to the surface. Remove from heat.
3. Use tongs to fish the onion out of the sauce and set it aside. 
4. Season sauce with salt to taste.
5. Preheat the oven to 375 degrees F.
6. Let the onion cool, then chop it very finely (or use a food processor for this). Place in a mixing bowl.
7. To the onion, add a generous pinch of salt, the beef, the egg, the garlic, the basil leaves and the pepper. 
8. Use hands to mix well. 
9. Form into golf ball-sized balls and place on an ungreased baking sheet. 
10. Bake for 16-20 minutes, until meatballs are cooked through, but juicy. Leave the oven on.
11. Spoon the sauce into a medium baking dish or oven-proof bowl. 
12. Nestle the meatballs into the sauce, pop in the oven for just a few minutes to heat well, then serve immediately. You may also divide the sauce and meatballs between ramekins or smaller oven-proof bowls for individual servings. 
13. Top with more basil and serve.