Preheat oven to 180 c.
Place the onion rounds on the base of your roasting pan then place the lamb on top (fat side up).
1 large brown onion
In a small bowl mix together olive oil, finely chopped rosemary, dried oregano, ground cumin, garlic and salt.
1 tablespoon olive oil, 2 teaspoon fresh rosemary, ½ teaspoon dried oregano, ½ teaspoon ground cumin, 3 garlic cloves, ½ teaspoon cooking salt
Rub the oil and herb mixture all over the lamb (including underneath) and pour the beef stock and water into the pan around the lamb.
250 ml beef stock, 250 ml tap water, 2.2 kg lamb shoulder
Bake uncovered for 30 minutes.
Turn the oven down to 100c, remove the lamb from the oven and cover it tightly with a layer of baking paper then 2 layers of foil (see my notes).
Bake for 12 hours or until lamb is super tender when checked (it should pull apart just with a fork).