Heat the olive oil in a large pot over medium heat. Add the lamb cubes and brown them on all sides for about 6 minutes. Remove the lamb and set it aside.
Add the onion to the same pot and cook until it softens, about 5 minutes. Stir in the garlic and cook for 1 minute more.
Return the lamb to the pot. Sprinkle in the sumac, za’atar, salt, and pepper. Stir to coat the meat evenly.
Pour in the lamb broth and bring the mixture to a simmer. Cover the pot and cook on low heat for 1 hour and 15 minutes, stirring occasionally.
Add the artichoke hearts, lemon zest, and lemon juice. Continue simmering uncovered for 20 minutes until the artichokes are tender and the broth has thickened slightly.
Ladle the stew into bowls and scatter the parsley over the top before serving.