For the marinade: Place the onions in a non-reactive container, add the salt, and use your hands to toss well. Allow to sit for 20 minutes for the onions to release their juices. Add the oil, yogurt, saffron water, pepper, and garlic, and mix well. Add the lamb and chicken, and toss well. Cover and allow to marinate in fridge overnight, and up to 24 hours.