Make Tomato Sauce next. Heat Olive Oil in a large frying pan or a pot over medium heat. Cook Onion and Garlic for 3-4 minutes or until soft. Add Tomato and Herbs, increase heat to high and bring to the boil. Then reduce heat to medium-low, add the meatballs and simmer gently, stirring occasionally, until the meatballs are cooked and the sauce thickens. Season with Salt and Pepper.