- 6 pounds red or black plums, pitted and coarsely chopped
- 4 pounds sugar (8 cups)
- 1/3 cup fresh orange juice
- 1/3 cup fresh lemon juice
- 2 tablespoons finely grated orange zest
Puree the plums in a food processor. In a large, heavy pot, mix the plum puree with the sugar and bring to a boil over moderate heat, skimming as necessary. Cook uncovered over low heat for 40 minutes, stirring occasionally.
Stir the orange and lemon juices and the orange zest into the plums; simmer until thickened, about 10 minutes longer. Pour the plum puree into 5 hot sterilized 1-pint jars, stopping 1/4 inch from the top. Wipe the glass rims and close the jars. Set them in a water bath and bring to a boil. Process for 20 minutes.