If you want a salted rim, run the lime wedge around the rim of a highball or rocks glass, then dip the rim into coarse salt spread on a small plate. Set the glass aside and chill briefly in the freezer or fill with ice to cool.

Combine and shake

In a cocktail shaker, add the blanco tequila (2 oz), fresh lime juice (0.75 oz), fresh grapefruit juice (1 oz), agave syrup (0.5 oz), orange liqueur (0.5 oz), and 2 dashes of Angostura bitters. Add 6 ice cubes, secure the shaker, and shake vigorously for 10–15 seconds until well chilled.

Strain and top

Discard ice from the prepared glass if you chilled it with ice. Double-strain the shaken mixture into the glass over fresh ice (large cubes or a single large sphere are fine). Top with 2 oz club soda to add effervescence. Gently stir once with a bar spoon to integrate the soda without flattening it.

Garnish

Express the oils of a grapefruit twist over the drink by holding the twist skin-side down and giving it a quick snap near the surface, then drop the twist or a grapefruit wheel into the glass. Optionally tuck a lime wedge on the rim.