Combine all the ingredients in a saucepan and cook, over medium-high heat, until boiling.
Reduce the heat to medium-low and simmer until the guava has dissolved and the sauce thickens to the desired consistency, about 10-15 minutes. Taste and adjust seasoning as needed.
Allow to cool to room temperature, and then serve or refrigerate in a sealed container for up to 1 week.
Notes
Cooking time will vary depending on the preferred consistency. I like mine thick, so it takes the whole 15 minutes to reduce. A thinner sauce will take less.
For a spicier sauce, increase the amount of cayenne. Or omit for a mild version.
The flavors deepen as the sauce rests in the fridge, so I recommend making it at least one day ahead, if you can!
The BBQ sauce will keep in the fridge for up to 1 week or in the freezer for up to 3 months.