Heat oil in medium-size saucepan over medium heat. Add onion and salt and cook, stirring occasionally, until soft, about 5 minutes. Add garlic and cook for 30 seconds. Stir in the remaining ingredients, bring to a boil, reduce heat, and simmer until thickened, about 30 minutes
Place mixture in a blender or food processor container and blend until smooth. Let cool before storing in the refrigerator for up to 1 month.