Remove the gizzards from the inside of the chicken and discard. Pat the outside of the chicken dry with paper towels.
Place the chicken, breast side up, on top of the onions. Cut the lemon in half and place it in the cavity of the chicken along with the fresh thyme and sage.
Use cooking twine to tie the legs of the chicken together and tuck the tips of the wings underneath the breast to prevent burning.
Rub the olive oil over the entire skin of the chicken and sprinkle with salt and pepper.
Roast this chicken in the preheated oven, uncovered, for 1 ½ - 2 hours or until the internal temperature of the chicken reaches 165˚ in the thickest part of the breast and the innermost part of the thigh and wing.
Let the chicken rest for 10 minutes before carving and serving with the drippings.
Notes
Cooking Time - The final cooking time will depend on the size of the whole chicken. Approximately 20 minutes per pound is recommended. If the skin starts to brown too quickly, place a piece of foil lightly over the chicken. Use a probe-style kitchen thermometer or instant-read thermometer to ensure the chicken is done cooking and doesn't dry out.
Onions - Celery, shallots, and leeks could also be used in combination with the onions, or as an alternative.
Complete Meal - Add red or yellow baby potatoes, brussels sprouts, carrots, or parsnips to the skillet around the chicken.
Italian-Style - Add Italian seasoning along with the salt and pepper. Crushed red pepper flakes could also be added.
Make Ahead - Prep and season the chicken up to 24 hours ahead of time. Cover the skillet with plastic wrap and store in the refrigerator until roasting time. Take out 30-60 minutes prior to roasting to come to room temperature and cook as directed.
Leftovers - Keep leftovers in an airtight container in the refrigerator for 3-5 days. Reheat in the microwave or oven with drippings or broth. Bones or carcass can be used to make homemade chicken stock