Instructions

Combine the sugar and water in a small saucepan; bring to a boil and stir to dissolve sugar. Cool completely.

Combine the grapefruit juice, zest and sugar/water mixture with the vodka and optional grenadine (for color) in a metal bowl. Chill in the refrigerator or by placing the metal bowl over a larger bowl filled with ice water until 40 degrees.

Pour chilled mixture into the container of an ice cream machine and churn until frozen.

Scoop frozen sorbet into a container. Seal and transfer container to freezer for several hours to allow sorbet to firm up. (Sorbet can be kept frozen for up to 3 days.)