Pommarola Summer Tomato Sauce
Pommarola is used as the summer tomato sauce, and should really be made strictly with fresh tomatoes.
Cut the tomatoes in half. Cut the onion, carrot, and celery into small pieces; do not chop them.
Place all the ingredients in a stock pot / InstantPot; do not add oil or water. Simmer, covered, very slowly for 1-1/2 to 2 hours, then pass everything through a food mill using the disc with the smallest holes. (If the sauce to be stored, do so at this point without adding anything else.)
Reheat the sauce (whether freshly made or stored), adding salt.
Note: Pommarola may be eaten with fresh or dried pasta, rice, or with topini. Only after the sauce is placed on these freshly cooked dishes should you add uncooked olive oil or butter and fresh pepper. On pasta or topini you also add freshly grated Parmigiano.