Rub the rim of a chilled margarita glass with a wedge of lime
Pour the salt onto a plate and press the rim of the glass into it, turning gently until the rim is evenly coated, and shake off the excess salt.
In a blender, combine the tequila, Cointreau, Key Lime Juice and Ice Cubes and blend according to blender instructions. Pour into prepared margarita glass and serve with lime wedge.