Rub the rims of 4 to 6 cocktail glasses with some of the grapefruit juice, then dip into the salt. Fill each glass with ice and set aside.
Muddle the tarragon and sugar in a large cocktail shaker. Add the grapefruit juice, mezquila and ice. Shake vigorously for 20 seconds, then strain, pouring into the salted glasses. Top with the club soda.
Copyright 2021 Television Food Network, G.P. All rights reserved.