Watermelon Granita

Cut about 1 pound watermelon into small chunks (discarding the rind), and freeze them. When they’re frozen, put them in a blender with 2 tablespoons sugar and 2 tablespoons lemon juice, and blend until the mixture liquefies. Pour the mixture into a shallow glass or ceramic pan, and freeze for about 2 hours, breaking up the ice crystals with a fork every 30 minutes or so. It should be slushy and crunchy.