Place all ingredients, except for salt, in a large saucepan and bring to a simmer over medium heat. lower heat and gently simmer for about 45 minutes, stirring occasionally to break up the tomatoes.
After 45 minutes, remove onion with a slotted spoon and break up remaining tomato chunks with a wooden spoon. Add salt to taste. This delicate sauce is delicious served over steamed or roasted vegetables, chicken or fish, or roasted spaghetti squash.