if you remember to, take the chicken out of its packaging the night before and salt/pepper the skin, and set it out uncovered in your fridge overnight to dry out. this will make crispier skin
preheat oven to 425
take chicken out of fridge if you dried it out, or take it out of its packaging and pat it dry now that you're doing it.
rub butter all over and salt/pepper the skin and inside the cavity
quarter the onion & lemon and put onion/lemon pieces inside the cavity. if you have any butter leftover put that in the cavity too.
tie up legs and put into cast iron skillet
optional: put some baby new potatoes into the skillet to roast alongside the chicken in its fat - mmmmmm. if you're doing that, about 30 min in, put the 1/2 c of white wine into the pan to hydrate/season the potatoes as they roast.
cook for about an hour, until the skin is medium brown