Preheat your oven to 400°F (200°C). Remove the giblets from the chicken cavity and pat the chicken completely dry inside and out with paper towels to ensure crispy skin.

In a small bowl, mix the softened butter, minced garlic, chopped rosemary, thyme, parsley, lemon zest, salt, and pepper until well combined to form an herb butter.

Carefully loosen the skin from the chicken breasts and thighs. Rub about two-thirds of the herb butter under the skin directly onto the meat, then rub the remaining butter all over the outside of the chicken. Squeeze the juice from the zested lemon over the chicken.

Stuff the chicken cavity with the quartered lemon, the remaining whole garlic cloves, and the quartered onion. Truss the legs together with kitchen twine and tuck the wing tips under the body. Place the chicken breast-side up in a roasting pan.

Roast for about 1 hour and 20 minutes, or until the juices run clear and a meat thermometer inserted into the thickest part of the thigh reads 165°F (74°C). Remove from the oven and let rest for 10-15 minutes before carving to allow the juices to redistribute.