In a medium saucepan, combine all of the ingredients and bring to a boil. Simmer over moderate heat until prunes are very soft, about 20 minutes. Discard the star anise pod, cinnamon sticks and whole cloves and lemon zest which have been placed in a cheesecloth sachet.
Pulse lightly the ketchup in a food processor. Season with salt and pepper.
Will keep for several weeks in the refrigerator. I put in 1/2 pint canning jars and process in hot water bath for 15 minutes.