If you enjoy a salted drink, prep the rim of your glass by rubbing a lime wedge or the sliced grapefruit along the rim. Dip in tequila salt, fill the glass with ice, and set aside.
Make the marg:
Fill a cocktail shaker with ice. Squeeze the juice from the grapefruit and pour it inside the shaker. Add tequila, Cointreau, and lime juice. Shake until the sides are fully frosted.
Serve:
Pour the shaken mixture into the prepared glass and garnish with a lime and grapefruit slice. Enjoy!