Run a grapefruit wedge around the rim of a highball or Collins glass. Spread the 0.25 tsp salt on a small plate and dip the rim into the salt to coat evenly. Set the glass aside.

Muddle chili

In a cocktail shaker, add the thinly sliced Thai chili (use half the seeds for medium heat or remove seeds for milder spice). Add the simple syrup (0.5 oz) and gently muddle 6–8 times to bruise the chili and release oils and heat. Let sit 30 seconds to infuse.

Build the cocktail

Add the El Jimador Reposado tequila (2 oz), fresh grapefruit juice (3 oz), and fresh lime juice (0.5 oz) to the shaker. Fill the shaker with ice (about 1 cup) and shake vigorously for 10–12 seconds until well chilled.

Strain and top

Double-strain the mixture into the prepared salt-rimmed glass filled with fresh ice (use a fine mesh strainer to catch chili bits). Top with grapefruit soda (2 oz) to add effervescence and adjust balance.

Garnish and finish

Express a grapefruit wedge over the drink (squeeze and rub the oils on the rim), then drop the wedge into the glass. Float a thin slice of Thai chili on top for presentation. If desired, finish with a light pinch of freshly cracked black pepper for an aromatic kick.

Adjustments

Taste and adjust sweetness or heat: add up to 0.5 oz more simple syrup or 0.25 oz agave if you prefer sweeter; muddle more chili or add a finely sliced extra piece for more heat.

Notes

For a lower-alcohol version, reduce tequila to 1.5 oz and increase grapefruit soda to 3 oz. Use freshly squeezed grapefruit and lime for best bright flavor. If grapefruit soda is unavailable, mix 2 oz club soda with 1 oz extra fresh grapefruit juice and a touch more simple syrup to taste.