Rim each glass with a lime wedge and dip in the coarse salt. Fill each glass with ice.
In a cocktail shaker, add the grand marnier, tequila, cranberry juice, lime juice and syrup and shake for 30 to 60 seconds. pour over the ice. Garnish with extra limes and fresh cranberries! Throw in a sprig of rosemary if you wish.
Stir together the water and sugar in a saucepan over medium heat. Whisk until the sugar dissolves and bring the mixture to a simmer. Remove from the heat and let it cool to room temperature.