Rub rim of a chilled margarita glass with lime wedge, and dip rim in salt to coat, if desired.
Pour lime juice, liqueur, orange juice, tequila, and powdered sugar over ice in a cocktail shaker. Cover with lid, and shake until thoroughly chilled. Strain into prepared glass. Add club soda or lemon-lime soft drink for a little fizz, if desired. Top with grenadine. Serve immediately.
*1/3 cup thawed frozen limeade concentrate may be substituted for fresh lime juice. Omit powdered sugar, and proceed with recipe as directed.
Note: For testing purposes only, we used Cointreau for orange liqueur and Jose Cuervo Especial for tequila.