Thoroughly sear the lamb in olive oil in a Dutch oven. Add onions; saute for 2 minutes; add garlic and saute for 1 minute. Add turmeric, nutmeg, cardamom, crushed red pepper and cinnamon; saute the mixture for 1 to 2 minutes more, being careful not to burn the onions or garlic. Add the tomatoes and beef stock and stir.
Cover the dish and bake at 350°F. for about 1 hour, until the meat is tender and begins to break up. Remove the dish from the oven and add the spinach, stirring until the spinach is wilted and blended in.
Allow the stew to cool slightly. Stir in the yogurt and lemon peel. Sprinkle with roasted pine nuts. Taste and add salt if needed.