Coat lamb with grated onion, ras el hanout, and salt and pepper. Marinate in refrigerator for 30 minutes or up to 2 hours. Melt 1 tablespoon butter in a wide, heavy-bottomed pan. Add meat, and brown lightly on all sides. Add saffron, water, and cinnamon stick; bring to a boil. Reduce heat to a simmer, and cook, covered, for 1 1/2 hours.