Drain tomatoes, reserving 1 tablespoon of the oil. Finely chop tomatoes. In a large saucepan, saute tomatoes and onion in reserved oil until onion is tender. Add garlic; cook 1 minute longer.
Stir in the water, stock, vinegar, sugar, basil, salt and pepper.
Bring to a boil. Reduce heat; cover and simmer for 30 minutes. Uncover; simmer for 15-20 minutes or until liquid has evaporated and mixture is the consistency of jam. Serve or transfer to an airtight container. Refrigerate up to 1 week.