1/3 cup water 1/3 cup sugar 1 teaspoon freshly minced ginger 3-1/2 lbs. cubed seeded watermelon 1 Tablespoon lemon juice
In a small saucepan, combine the water, sugar and ginger. Cook over medium heat, stirring occasionally until sugar is dissolved, about 4 minutes. Transfer the syrup to a bowl, and set it in a larger bowl filled with ice. Stir syrup until cool.
In a blender, working in batches, puree the watermelon and sugar syrup. Pour puree into a bowl. Repeat with remaining watermelon and sugar syrup. Stir in the lemon juice. Transfer the mixture to a ice cream maker and freeze according to manufacturers directions. Once the mixture is very slushy, transfer to the freezer. Serve using an ice cream scooper.