Mix oil with honey (if using), spices, salt, and pepper in a large bowl, then add chicken and onion, tossing to coat. Arrange chicken, skin side up, and onion in a 3-quart shallow baking dish. (If you have the time, let the chicken marinate for a while).
Bake until chicken is just cooked through and skin is golden, about 30 minutes. Skim any fat from pan juices in dish.