Trim excess fat and gristle from meat and cut lamb into 1-inch cubes. Place meat in a large bowl. In a small bowl, mix the cumin, ginger, cinnamon, and saffron; sprinkle over the meat and set aside.

On a cutting board, mince together the orange zest, cilantro leaves, garlic, and salt until you have a paste. Add to the meat along with the orange juice and stir well to coat. Cover the bowl and let stand at room temperature for 2 hours, or up to overnight in the refrigerator.

Transfer the mixture to a heavy pot, add the onions, tomatoes, and 1 cup water. Bring to a boil, cover, reduce heat, and simmer (or bake in a preheated 350 degree oven) until the meat is very tender, about 1 1/2 hours. Add olives and, if using, preserved lemon to the pot. Cook about 10 minutes more, then serve.

Preserved Lemons:

Wash a 1-pint glass-canning jar and its lid with hot soapy water; rinse and dry thoroughly.

Cut 6 of the lemons, 1 at a time, into quarters through 1 end without cutting all the way through the other end. You want the lemon to open out like a flower, but not to separate. Place the lemon on a large piece of parchment or waxed paper, spread quarters open and sprinkle flesh with a heaping tablespoon of kosher salt; put the lemon into the jar. Continue with remaining lemons, sprinkling salt on each. Pack the lemons in the jar tightly, filling it to the top (you may need more or less than 6 lemons, depending on their size). When you reach the top, lift the parchment and pour the excess salt from it into the jar of lemons.

Slide the bay leaves down opposite sides of the jar. Juice the remaining lemons 1 by 1, adding juice to the jar, until it reaches the top. Seal jar, shake well, and let stand at room temperature, shaking well every 12 hours, for 1 week. After 1 week, transfer jar to the refrigerator, continuing to shake every day. Lemons are preserved after 3 weeks and keep up to several months in the refrigerator.

To use lemons, pull out as needed and scrape away pulp. Dice peel and use as a condiment.