Quick Plum Preserves

Coarsely chop plums and stir together with sugar, water, and cinnamon stick in a 2-quart heavy saucepan. Simmer, uncovered, stirring occasionally (more often toward end of cooking to prevent sticking), until thickened and reduced to about 2 1/2 cups, 45 minutes to 1 hour. Discard cinnamon stick and cool preserves. Transfer to an airtight container and chill, covered.