Using a vegetable peeler, remove the zest in strips of 2 lemons and 2 limes, preferably organic. Transfer the zests to a shallow medium bowl; add 4 kaffir lime leaves and 2 rosemary sprigs. Add 1 cup sugar and muddle the ingredients until the zests begin to release their oils. Push the zests to the sides of the bowl, cover and let macerate overnight. Refrigerate for up to 2 weeks.