2 pounds red or black plums (about 12 medium or 10 large)
2 Tablespoons sugar
3⁄4 cup cold water
3⁄4 cup sugar
1⁄2 teaspoon lemon juice
1 Tablespoon vodka, white gin or Triple Sec (optional)
Preheat the oven to 350 degrees F. Line a rimmed baking sheet with foil or parchment paper.
Cut plums in half and remove the pit. Arrange plums on prepared baking sheet and sprinkle with the 2 tablespoons sugar. Roast for 30 to 35 minutes or until the edges of the plums start to caramelize and plums are juicy and tender. Let plums cool.
Place cooled plums in a large bowl. Blend the plums with an immersion blender or a food processor.
Next make the simple syrup. Place cold water and sugar in a small saucepan. Bring to a boil over medium heat; stir with a wooden spoon to dissolve sugar. Simmer for 2 to 3 minutes and remove from the heat. Add in lemon juice and alcohol; mix well. Add simple syrup to the blended plum mixture; allow mixture to cool.
Pour mixture into a 9x13-inch cake pan, cover, and chill in the refrigerator for one hour. Next, place chilled plum mixture in the freezer. Every hour for the next 4 hours, remove the plum mixture and whisk it to break up the ice crystals. Once the sorbet is frozen, break it into chunks with a metal spoon and transfer to a food processor and pulse until smooth and light. Pour into a resealable container, cover, and freeze until firm (about 4 hours).
Before eating, remove the sorbet from the freezer 5 to 10 minutes beforehand to make scooping easier.