Pour salt onto a flat rimmed dish. Moisten the rim of two margarita glasses with a lime wedge; dip in salt. Combine Mango Purée (recipe below), Lime Sour, tequila and Cointreau in a cocktail shaker over ice. Shake to combine; pour into prepared glasses. Garnish each glass with a lime twist.
MANGO PURÉE: In a food processor, purée 10 oz. peeled fresh mango, 1/4 cup pure mango juice and 1 oz. fresh squeezed lime juice until smooth; strain if desired.