Wash the orange, then zest the rind. Squeeze the juice and soak the apricots in the juice to swell.
Heat the oil in a large, heavy-based casserole and brown the onion for around 10 minutes, stirring from time to time.
Add the meat, cumin, cinnamon and salt and pepper to taste and stir well for 5 minutes. Pour in the orange juice with the apricots, orange rind, almonds and water. Cover, and bring to a simmer over a medium heat. When the juice is bubbling, lower the heat and continue to cook, stirring from time to time, for about 40 minutes, or until the lamb is cooked.
Meanwhile, dry-toast the sesame seeds in a frying pan. They should become golden but not blackened.
Transfer the cooked lamb to a serving platter and sprinkle with the sesame seeds and coriander, if using.