Prepare the Dish: Place the lamb shoulder into your baking dish along with the potatoes, onions, and cleaned garlic cloves.
Season and Coat: Pour in the olive oil, then gradually add the salt, pepper, cinnamon, and cumin while mixing to ensure the lamb and vegetables are evenly coated with the seasonings.
Add the Tomatoes: Blend the tomatoes until smooth and pour them over the lamb and vegetables. Mix again to distribute the tomato sauce evenly throughout the dish.
Cover the Dish: Cover the baking dish with a layer of wet parchment paper (soaked and wrung out) to prevent it from touching the foil. Tightly seal with aluminium foil to retain moisture and steam.
Bake: Place the dish in a preheated oven at 180°C (fan-forced) and bake for 4 hours (see notes below).
Rest and Serve: Allow the dish to rest for 10 minutes before serving. Serve hot with crusty bread or your favourite sides.