How to Make It
To make the syrup, combine all syrup ingredients in a small saucepan over medium high heat; bring to a boil. Turn heat to medium and stir occasionally until sugar melts, salt is almost melted and mixture becomes syrupy. Strain syrup to remove any small salt crystals that remain. Cool to room temperature and store in a glass jar in the refrigerator for up to 2 weeks.
To make the cocktail: chill a 5 ounce martini glass in the freezer for 20 minutes. While glass is chilling, combine bourbon, salted sugar syrup and grapefruit juice in a cocktail shaker with ice cubes. Shake vigorously for 30 seconds and strain mixture into frozen martini glass. Garnish with twist and serve immediately.