Remove the pits from the plums and slice them. Place the sliced plums in a medium saucepan with 1/4 cup water. Cover and cook on medium heat, occasionally stirring, until the plums are soft and fully cooked. Let it cool to room temperature after removing it from the heat.

Puree the cooled plums until smooth. You should get around 2 cups of plum puree.

In the same saucepan, mix the sugar (or sugar and corn syrup) with about 1/2 cup of the plum puree. Cook on medium heat, stirring continuously until the sugar is fully dissolved. Remove from heat and combine with the rest of the plum puree. Add the kirsch or maraschino and a few drops of lemon juice, then chill the mixture thoroughly, preferably overnight.

Once chilled, freeze the sorbet in your ice cream machine according to the manufacturer's instructions.