adapted from David Lebovitz's Mirabelle Jam; makes one 8 oz. jar
Add the plums, sugar, and lemon juice to your pot and add water to about 1/4-inch depth. Cook over medium heat, stirring frequently, until thickened. (You can eye-ball it, but you're going for about 218 - 220°F on a candy thermometer (adjust down about 10 degrees for 5000 ft. elevation).)