For sauce: In a medium-sized pot, heat olive oil over medium heat. Add onion, and reduce heat to medium low, stirring until onions are soft, 10–12 minutes. Add garlic, and cook 2–4 minutes, until aroma is released. Add tomatoes; stir to combine.
Pour water into tomato container, and swirl to dissolve any remaining tomato. Add water to pot. Increase heat to medium-high, and when sauce starts to boil, reduce to medium-low to maintain a slight bubbling in center of sauce.
Add basil, salt and red pepper flakes; stir to combine. Simmer 30–40 minutes. Stir, taste, and
adjust seasoning as needed. If sauce gets too thick, add water ¼ cup at a time. Remove and discard garlic and basil sprigs.
For meatballs, preheat oven to 450°. In a large bowl, thoroughly combine all ingredients. With clean, wet hands, form mixture into 10 meatballs by rolling between the palms of your hands.
Place meatballs in a large baking pan with a small amount of water—just enough to coat the pan. Cook 25 minutes or until done. Keep an eye on pan, and add water if needed.
Serve two meatballs per person, with a generous dollop of sauce.