Transfer onion and garlic to a saucepan, add remaining ingredients and bring to the boil. Reduce heat and allow to simmer uncovered until reduced by half.
Notes
I prefer to make this sauce the day before so that it can cool completely. This also gives the flavors plenty of time to mesh and develop. It will store well in the refrigerator for 2-3 weeks, if it lasts that long.
Recipe by My Earth Garden at http://www.myearthgarden.com/2012/07/perfect-homemade-bbq-sauce/