In a 1.5 litre saucepan, combine paste and water over medium heat. Stir paste while separating with a wooden spoon and bring sauce to a boil. Reduce heat and simmer until sauce thickens to coat the back of a spoon.
Remove the pan from the heat and strain the sauce into a bowl. Discard the skin and any stray seeds, return the tamarind sauce to the pan over medium heat.
Add remaining ingredients. Reduce heat and simmer for about 15 minutes. Let cook, store in a sterilized glass jar or an airtight container in the refrigerator for up to two weeks. Use as a glaze on chicken, pork or beef.
Guava barbecue sauce:
To prepare the sauce, in a small saucepan, add paste and water over medium heat and combine thoroughly to make a sauce that coats the back of the spoon. Stir and let simmer for five minutes.
Reduce heat to low and add remaining ingredients. Stir and let simmer for five minutes.
Brush or spoon the sauce over grilled chicken or pork.