Preheat your oven to 425ºF. Stuff the cavity of the chicken with the lemon. Place chicken breast side up. Brush softened butter on outside of chicken and top with thyme, salt and pepper. Roast until juices run clear, about 1 1/2 hours. Let rest 10 minutes before slicing and serving.
You can tie the legs of the chicken together with kitchen twine but it is not essential.
If the top is getting too brown, cover with aluminum foil and continue cooking.
Serve this Perfect Roast Chicken with Herb Roasted Potatoes and Asparagus.