Combine all ingredients in to a medium sauce pan, and bring to a simmer. Crush tomatoes against side of pan with a slotted spoon while the sauce cooks.
Adjust salt and pepper to taste, and cook for about 40 minutes. If seeking a deeper flavor cook up to 2 hours. Remove onion after cooking.
Notes
Can be made ahead, and stored for up to a week. May be frozen for up to one month.Â