1. Rub rim of a chilled margarita glass with lime wedge, and dip rim in salt to coat, if desired.
2. Fill cocktail shaker half full with ice. Add lime juice, liqueur, tequila, and powdered sugar; cover with lid, and shake until thoroughly chilled. Strain into prepared glass. Garnish, if desired, and 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 Midori for melon liqueur and Jose Cuervo Especial for tequila.