Rub rim of a chilled margarita glass with lime wedge, and dip rim in margarita salt. Fill a cocktail shaker half full with ice. Add powdered sugar, lime juice, liqueur, and tequila. Cover with lid; shake until thoroughly chilled. Strain into prepared glass.
Drop In: Cilantro. A staple of Mexican cuisine, this herb complements the often peppery flavor of tequila. Or give basil a try instead.