Preheat oven to 450 degrees
Empty out roasting chicken and place chicken breast up in a roasting or baking dish, pat dry
Sprinkle the inside of the chicken liberally with salt
Stuff the chicken with the onion and apple chunks
Sprinkle leftover apple and onion in the baking dish around the chicken
Rub the softened butter on the chicken and sprinkle on salt and pepper
Pour the apply cider into the pan, it should be roughly 1-2 inches deep
Bake uncovered at 450 degrees for 10-15 minutes
Reduce temp to 350 and bake for 20 minutes per pound
When the chicken is done, transfer the liquid from the pan to a sauce pot/pan and bring to a boil
In a small cup or dish, mix the corn starch and water/apple cider together
Add to the boiling liquid and stir until thickened
Remove from heat
Serve immediately
I prefer to not use a rack in my roasting pan/baking dish. I think the meat gets more flavor sitting in the liquid