Drain the tomatoes, reserving their juice. Strain the captured juice to hold back the seeds. Using your fingers, push out the excess seeds from each tomato. Chop the tomatoes and set the tomatoes and juice aside. If using pancetta, chop it finely. If using bacon, drop it into boiling water to cover and blanch for 30 seconds. Drain, rinse in cold water, and drain again. Chop finely.

In a saucepan over medium heat, warm the olive oil. Add the onion. Sauté the onion until it is translucent, about 3 minutes. Add the pancetta or bacon; reduce the heat to medium-low and sauté until the onion is totally softened and the pancetta or bacon has colored, about 8 minutes or so. Add the ground meats, parsley, basil, and sage and sauté until the meat is colored but not hard, about 2 minutes. Add the tomatoes and juice and the tomato paste. Stir well and simmer, still over medium-low heat, for 5 minutes; then stir in the wine or water. Cover partially and simmer over the gentlest possible heat until the liquid thrown off by the tomatoes is evaporated and a thick sauce is formed, about 1 hour, adding water if necessary to prevent the sauce from becoming dry. Season with salt and pepper.