Bring all ingredients except plums to a boil in a non-aluminum pan. Stir in plums. Simmer until thick, stirring often. Mash with a potato masher or blend if you want a smoother sauce.
To can: Fill hot, clean jars with hot sauce, leaving 1/4" headspace. Wipe rims, adjust lids and process in a boiling water bath for 20 minutes at 0-1000 ft., 25 minutes, 1001-6000 ft., or 30 minutes, above 6000 ft. Makes about 6 half pints.