Pat the racks of lamb dry and trim away any excess fat from the fat cap. Season them all over with salt and freshly cracked pepper, set them in a large baking dish, and set aside.
Make the chermoula sauce. In a high-powered blender, combine the chopped cilantro, parsley, garlic, toasted cumin & coriander, preserved lemon, and urfa and top with the olive oil. Blend on high until very smooth, then season to taste with salt and pepper.
Marinate the lamb. Pour 2/3 of the marinade over the racks of lamb and use your hands to massage the marinade into the meat. Cover, and refrigerate for 4-8 hours. Store the rest of the marinade in an airtight container in the fridge to be served with the lamb.
Prep the grill. Preheat an outdoor grill over medium heat to 450 F. Let the grill preheat for a full 15 minutes. Make sure the grates are cleaned of any debris and lightly grease them with oil or nonstick cooking spray. After the grill is preheated, turn off one side of the grill. If you're using a charcoal grill, make sure the lit charcoal are arranged only on one side of the grill.
Grill the lamb. Place the racks of lamb over the direct heat portion of the grill, fat cap side down, cover, and sear for 5 minutes. After the initial sear, flip the racks over and transfer them to the cooler side of the grill for about 15 minutes, or until a meat thermometer reads about 135 F (for medium). Transfer the racks of lamb to a plate, loosely tent with foil, and let them rest for 10-15 minutes.
Serve. Cut the racks of lamb into chops, sprinkle them with flaky sea salt, and serve with more chermoula sauce on the side.