Add all the ingredients to your blender or food processor and process until completely reduced to a fine, liquid puree.
Transfer that puree to a medium saucepan and bring to a boil. Lower the heat, partly cover and simmer for 45 to 60 minutes, stirring from time to time, until the sauce is nice and thick and darker in color.
Kill the heat and let the sauce come down to room temperature.
If you want a really smooth BBQ sauce, pass it through a fine mesh sieve (you will have to help it through by swirling it around with a ladle), otherwise, just transfer it straight to an airtight container and refrigerate.
This BBQ sauce gets better after sitting in the fridge for a few days and it will keep for 2-3 weeks in the refrigerator.