- Make a sugar syrup by mixing two cups of sugar into four cups of the water then bringing this mixture to a boil. Cook for 5 minutes or until sugar is dissolved and syrup appears slightly thick. Set aside to cool.
- Toss watermelon with remaining ½ cup of sugar and salt. Let rest for half an hour. Purée with a food mill or food processor. Mix purée with two cups of water and lemon juice. Toss in reserved seeds for aesthetic appeal.
- Churn in an ice cream maker according to the instructions and serve or store in freezer.