These meatballs harbor a secret: their sauce is on the inside! You soften onion, garlic, tomato and zucchini in olive oil and then fold it into the meat for meatballs that are tender and juicy enough to eat all on their own -- though they're worthy companions for a batch of your favorite sauce as well. —Merrill Stubbs
In a medium sauté pan, warm 2 tablespoons of olive oil over medium heat. Add the onion and a large pinch of salt and cook, stirring frequently, until the onion starts to soften, 3 to 5 minutes. Add the garlic, tomatoes and zucchini, and a few more pinches of salt, and continue to cook until the vegetables are very soft, and most of the juices from the tomatoes and zucchini have cooked off, about 8 to 10 minutes. Set aside to cool.
In a large bowl, combine the meat, breadcrumbs and Parmesan. Work everything together gently using two forks -- be careful not to over-mix. Then, using your hands, gently work in the egg and the cooled vegetables until just combined.
Shape the mixture into 1 1/2-inch meatballs. Heat a thin layer of olive oil in a large frying pan over medium heat and add about half of the meatballs, making sure not to crowd them. Brown them on all sides, turning them with tongs, and then cover and reduce the heat to low finish cooking (they should take 5 to 8 minutes total). Drain the meatballs on paper towels, add a little more oil to the pan and cook the rest of the meatballs. Serve the meatballs on their own, or warm them in a pot of your favorite sauce.