In a large heavy pot heat the oil until shimmering. Add the onions and garlic, and cook 5 to 7 minutes until the onion has gone translucent. Stir in the tomato puree, the tomatoes, the salt, parsley, basil, oregano, red pepper flakes. Add water to reach your desired consistency. Add the sausage or meatballs to the pot and simmer for about 2 hours.
Remove the meat from the pot with a slotted spoon. Chill the sauce completely before storing the sauce in covered containers in the freezer.
This supply of homemade red sauce lasts us about 5 weeks once frozen. I store it in plastic containers with lids or in mason jars in the freezer.