Step 1

Slice the grapefruit in half widthwise. Using a citrus juicer, reamer, or the tines of a fork, juice one half of the fruit and set aside. Cut the other half into 1/2" slices.

Step 2

Spread kosher salt onto a small plate and shake to create an even layer of salt. Run one of the grapefruit slices along the rim of the glass, then dip the glass into the salt to create a salt rim. Fill the glass with ice and set aside.

Step 3

Fill a cocktail shaker with ice. Add the grapefruit juice, tequila, lime juice, and simple syrup or agave nectar. Stir to combine all ingredients.

Step 4

Pour the cocktail into the prepared cocktail glass. Top with soda water to your preference and garnish with a grapefruit wedge. Serve immediately.