Rub the rims of 2 martini glasses with a lime wedge, then dip the rims in a dish of course salt. Refrigerate the glasses if desired.
In a shaker, combine the lime juice, tequila, and orange liqueur. Add ice and shake 10 to 15 seconds, then strain into the prepared glasses.
Recipe courtesy of Rick Bayless. From Rick Bayless's Mexican Kitchen; Scribner, 1996.