Cut the watermelon into small one-inch cubes. Remove any seeds and place the pieces on a parchment-lined baking sheet.

Spread the watermelon pieces into one layer. Freeze for at least four hours until completely solid.

Add the sugar and water to a small saucepan. Heat gently until the sugar completely dissolves.

Remove the saucepan from the heat. Let the simple syrup cool completely before adding it to the blender.

Place the frozen watermelon cubes into a high-powered blender or food processor.

Pour the fresh lime juice over the frozen watermelon. Fresh lime gives the sorbet a bright flavor.

Add the cooled simple syrup to the blender. Start with the recommended amount and adjust sweetness later.

Add a small pinch of kosher salt. It helps balance the sweetness and enhances the watermelon flavor.

Blend everything until completely smooth. Stop occasionally and scrape the sides if necessary.

Add the vodka if desired. A small amount can help keep the frozen sorbet easier to scoop.

Pour the mixture into a freezer-safe container. Freeze for one hour, then stir thoroughly with a fork.

Repeat the stirring process every forty-five minutes for two or three rounds. Freeze until firm and scoopable.