Heat olive oil in a large saucepan and add purée. Bring to a boil, then reduce heat to maintain a rapid simmer. Form bite-size balls of meat mixture, about 1 level tablespoon each, and gently drop into simmering sauce. As they begin to pile up, gently shake and swirl pan from time to time, to help them slip under sauce. (Do not stir with a spoon, as they will still be soft.) When all meatballs are in sauce, lower heat just enough to prevent scorching, season to taste, and cook for about 15 minutes, until meatballs are cooked through and sauce has thickened. Slide a spatula under them from time to time to keep them from sticking. Serve at once, or place in slow cooker to keep warm.