1. In a small bowl, thoroughly combine all the spices. Remove giblets from chicken, clean the cavity well and pat dry with paper towels. Rub the spice mixture into the chicken, both inside and out, making sure it is evenly distributed and down deep into the skin. Place in a resealable plastic bag, seal and refrigerate overnight.
2. When ready to roast chicken, stuff cavity with onions, and place in a shallow baking pan. Roast, uncovered, at 250° F for 5 hours. After the first hour, baste the chicken occasionally (every half hour or so) with pan juices. The pan juice will start to caramelize on the bottom of the pan and the chicken will turn golden brown. Let chicken rest about 10 minutes before carving.