Run a lime wedge around the rim of a glass. Dip the edge of the glass in kosher salt and fill with ice.
Add the tequila, grapefruit juice, and lime juice. Stir to combine.
Top off with sparkling water and garnish with a lime wedge.
Notes
Use fresh ingredients: For the best flavor, use fresh grapefruit and lime juice. Bottled juices can be used in a pinch, but fresh juice will make a noticeable difference.
Adjust to taste: Feel free to adjust the sweetness and tartness of your Paloma. Add some sweetener like agave nectar or simple syrup if you like, or more lime juice for extra tartness.
Chill your ingredients: For a truly refreshing drink, make sure all your ingredients are well-chilled before mixing.