Brush the maple syrup over the rims of two tumblers or margarita glasses (alternatively, drizzle a little onto a shallow plate and dip the rims in). Combine the demerara or golden granulated sugar and pinch of sea salt flakes on a plate or saucer, and dip the rims into the mixture to coat. Chill the glasses while you make the cocktail. Pour the tequila reposado, triple sec, maple syrup, lime juice and freshly squeezed clementine juice into a cocktail shaker. Add a handful of ice cubes, and shake until the outside of the shaker feels very cold. Fine-strain the cocktail into the prepared glasses and fill with fresh ice cubes before serving.
