Preheat the oven to 425*.
Gather your quartered lemons, onion slices, peeled garlic, thyme sprigs, grind your pepper and set aside salt ready to put your dish together.
Rinse whole chicken inside and out. Pat it dry.
Salt and pepper the inside of your chicken.
Stuff your lemons, garlic, and thyme inside the chicken. Tie the legs together with kitchen string or twine if you have it.
Toss your onions into your roasting pan with a few glugs of olive oil, toss them around. Rest chicken on top.
Brush the outside of the chicken with 2 tablespoons of melted butter. Salt and pepper the outside of chicken.
Cook for 1 hour and 15 minutes at 425°. If using croutons, you can make them now or at the end while the chicken is resting. When the chicken reaches the 1 1/4 hour point, I like to check the chicken's temperature in the breast meat. If it reads 180°, then it is done. If it's not 180°, then put it back in for 10-15 more minutes and check it again. A 4-5 lb chicken usually takes about 1 1/2 hours total and has the perfect golden crisp skin. When it is done, I let it rest in the pan for another 15 minutes.
If serving with croutons, spread out croutons on serving platter. Cut chicken into serving pieces, or keep whole, and set on top of croutons. Pour pan juices and onions over the chicken and croutons and serve.