This dish can be simplified or made more elaborate depending on your taste. You can omit the onions and simply season the meat with the fennel spice. You can roast aromatic vegetables until caramelized and add them to the bottom of the roasting pan. Or you can add another layer of flavor to the onions: mince fresh rosemary and fruits such as oranges, kumquats, Meyer lemons, apples, pears, or quince, and cook with the onions, or make a paste of garlic and fresh or dried chiles and add to the onions.