Zest the lime. Combine the lime zest and margarita salt in a shallow bowl or small, flat plate. Moisten the rim of a glass with lime juice. Dip the glass in the lime salt to coat the rim. Set aside.
Pour cranberry juice, tequila, triple sec and maple syrup into a cocktail shaker. Shake vigorously for 15-20 seconds.
Fill the glass with ice. Pour the margarita into the glass. Top off with club soda. Garnish with a lime wedge and fresh cranberries, if desired.