Rub the grapefruit wedge around the rim of an old-fashioned glass. Pour the coarse salt or Tajín onto a small plate and press the wet rim into it to coat. Set the glass aside.

Fill the prepared glass with cubed ice and set aside so it stays chilled while you mix the drink.

Build the Cocktail

In a cocktail shaker, add the jalapeño slice and cilantro leaves. Gently muddle 6–8 times — enough to release oils and aroma but not so much that the cilantro becomes pulverized and bitter.

Add the reposado tequila (3 oz), fresh lime juice (1 oz), fresh grapefruit juice (1 oz), orange liqueur (0.5 oz), and agave syrup (0.25 oz) to the shaker.

Add 2 dashes of Angostura bitters to the shaker to add depth and a touch of aromatic spice.

Fill the shaker with ice until about two-thirds full. Secure the lid and shake vigorously for 10–15 seconds until the outside of the shaker is cold and slightly frosted.

Finishing & Serving

Double-strain the cocktail into the chilled, rimmed old-fashioned glass over the fresh ice using a cocktail strainer and a fine mesh strainer to catch small bits of jalapeño and cilantro.

Garnish with a grapefruit wedge or expressed grapefruit peel (run the peel around the rim and squeeze over the drink to express oils) and a small cilantro sprig. If you like more heat, float an additional thin jalapeño round on top.

Serve immediately. Taste and adjust: if the drink is too tart, add another 1/4 oz agave; if too sweet, add a splash more lime (about 1/4 oz).