Mix the chopped rhubarb and water in a small saucepan with a lid. Simmer on low until tender, 5 - 10 minutes. Cool.
Purée the cooled rhubarb in a blender or food processor.
Mix the puréed rhubarb with the rest of the ingredients.
Refrigerate until use. Yields approximately 1 1/2 cups. The bbq sauce is delicious on chicken or pork.