Heat up your tajine, if you don’t have a tajine, use a deep pan with a cover. Add a bit of oil to the tajine, cook the onions until caramelized then add in the meat. Let the lamb sear on one side then turn the lamb around, add the water and the cinnamon stick and bring to a boil, then lower the heat to the lowest setting and cover. Let it simmer for 2 hours. Do not lift the cover until the 2 hours has passed. After 2 hours add in the prunes, and let the tajine cook, uncovered for another 20 minutes.