Run a lime wedge around the rim of a glass. Invert glass and dip rim in a shallow plate of kosher salt until entire rim is covered in salt. Set aside.
Place mango nectar, tequila, Cointreau, lime juice and simple syrup in a cocktail shaker filled with ice. Shake vigorously for at least 30 seconds.
Pour margarita into prepared glass. Garnish with additional lime wedge, if desired.
