Vegetable oil, for deep-frying
1 pound clean squid with tentacles, bodies cut into 1/3- to 1/2-inch-thick rings
2 cups all-purpose flour
2 tablespoons dried parsley
Salt and freshly ground black pepper
2 lemons, cut into wedges
1 cup simple tomato sauce, recipe follows or jarred marinara sauce, warmed
1/2 cup extra-virgin olive oil
1 small onion, chopped
2 cloves garlic, chopped
1 stalk celery, chopped
1 carrot, chopped
Sea salt and freshly ground black pepper
2 (32-ounce) cans crushed tomatoes
2 dried bay leaves
4 tablespoons unsalted butter, optional