Slice onion and place evenly over the bottom of a cast iron skillet. Make sure the skillet is bigger than the chicken. (12" - 15" skillet will work)
Remove gizzards from the inside of the chicken and discard. Place chicken breast side up on top of the sliced onions in the skillet. Pat the chicken skin dry with a paper towel.
Cut the lemon in half and place into the cavity of the chicken along with the fresh thyme and sage.
Use cooking twine to tie the legs of the chicken together and then tuck the tips of the wings underneath the chicken breast to prevent burning.
Rub olive oil over the entire skin of the chicken and sprinkle with salt and pepper.
Place the entire skillet in the pre-heated oven and roast for 1 ½ - 2 hours or until the temperature of the chicken reaches 165˚ in the thickest part of the breast and thigh with a kitchen thermometer. If the skin starts to brown too quickly, a piece of foil can be placed over the top of the chicken towards the end of the cooking time to prevent burning.
Once the chicken is done cooking, remove it from the oven and let it rest for 10 minutes before carving. Serve in the skillet with drippings.
Notes
Cooking times will vary depending on the oven and size of the chicken. The suggested cooking time is approximately 20 minutes per pound.