1/4 cup kosher salt
1 wedge lime
2 tablespoons (1 ounce) fresh lime juice
2 heaping teaspoons superfine sugar
1 tablespoon (1/2 ounce) Cointreau or other triple sec orange liqueur
1/4 cup (2 ounces) reposado tequila
About 2 cups ice cubes
Spread salt on small plate. Rub lime wedge halfway around rim of 10-ounce glass (such as double old-fashioned). Dip moistened side of glass in salt to lightly coat. Set aside. In cocktail shaker, stir together lime juice and sugar until sugar partially dissolves (about 5 seconds). Add Cointreau, tequila, and 1 cup ice cubes. Shake vigorously for 25 seconds, then strain into prepared glass. Fill glass with remaining ice cubes.