2 pounds small plums (such as Italian prune plums), pitted and cut into 1/2-inch wedges
1 1/2 cups sugar
1/2 lemon, seeded
- In a large, nonreactive saucepan, toss the plums with the sugar and let stand, stirring occasionally, until the sugar is mostly dissolved, about 1 hour.
- Squeeze the lemon over the plums, add it to the saucepan and bring to a boil, stirring until the sugar is dissolved. Cook over moderate heat, stirring, until the liquid runs off the side of a spoon in thick, heavy drops, 20 to 25 minutes. Skim off any scum that rises to the surface of the jam.
- Discard the lemon and spoon the plum jam into three 1/2-pint jars, leaving about 1/4 inch of space at the top. Close the jars and let the jam cool to room temperature. Store the jam in the refrigerator for up to 3 months.