Over medium heat in a saucepan, cook the chopped plum, brown sugar, garlic, ginger, vinegar, cloves, and cayenne powder until it reaches a boil, then reduce the heat to low.
Simmer the mix for 20 minutes, stirring frequently, until the plum softens and the sauce thickens to your desired thickness.
Remove the sauce from the heat and add the soy sauce. Stir to combine.
Allow the sauce to cool to room temperature, then using a food processor, process the sauce to your desired smoothness (optional if you like the sauce a little chunky).
Use immediately, or for best flavor refrigerate overnight in an airtight container to allow the flavors to meld.