I finally attempted the homemade sauce using a bumper crop of 4 types of tomatoes. I squeezed as much juice before I pureed, and have simmered only 3 hours. I know I have several more hours to go, but I have a few questions. Do I simmer with lid on or off? The sauce is looking a bit watery, what can I do to thicken. I know tomato paste, but what else? Cornstarch, flour, or will these kill it? Please help, I really wante to shock my sce loving husband!?