Chop one large onion and saute in oil in a large pot for a few minutes until soft. Add 3 cloves of minced garlic the last couple of minutes but be careful not to let it burn.
Add 24 ounces of tomato sauce (3-8 ounce cans), 18 ounces of tomato paste (3-6 ounce cans), 3 cups water, 3 teaspoons oregano, 3/4 teaspoons basil, 3 teaspoons sugar, and 3/4 teaspoons pepper.
Let it simmer slowly for about half an hour. It will thicken. Taste and adjust seasonings as needed. This makes 2 quarts of sauce that you can freeze it in batches if you want.