Chicken with Caramelized Sumac Onions, Preserved Lemon, and Israeli Couscous

I recently became inspired while flipping through the Ottolenghi cookbook, Jerusalem. I wanted a hearty chicken dish for dinner and, though none of Yotam's recipes sounded perfect, his Roast Chicken with Sumac, Za'atar, and Lemon served as a marvelous foundation for this one-pot stew. It's fairly qu...