I found this recipe in Deborah Madison's book Vegetarian Cooking for Everyone as I was looking for a low carb barbecue sauce. It has a good flavor, but is more of a vinegar based barbecue sauce then the sweeter sauces that are produced commerically.
Mix all the ingredients in a saucepan and bring to a simmer.
Reduce heat to low, cover and simmer for about 15-20 minutes until thickened and onions are moistened.
NOTE: You can use this warm or cold and it will last in the refrigerator for several weeks.
NOTE: you can also add 2-3 tablespoons brown sugar if you like it sweeter. My second batch, I added SPLENDA brown sugar.to give it a sweeter taste and to also keep it low carb.