Puree watermelon in a food processor or blender until smooth

MAKE SIMPLE SYRUP - in a saucepan combine water and sugar, bring to a boil then simmer until sugar dissolves and mixture becomes clear, about 2 minutes

combine watermelon puree, lemon juice and salt in a large pitcher.

Pour warm simple syrup over watermelon mixture and stir well.

Chill until very cold, at least 2 hours

SUGAR FROST RIM OF GLASS - Place sugar in small bowl or plate. rub the lemon slice around the rim of the glass to wet it. Dip glass rim in sugar to coat the rim. Chill glass until ready to serve

Serve in frosted chilled glass over ice