Step 1

Preheat oven to 450°F.

Step 2

Pat the chicken dry with paper towels and place in a large roasting pan.

Step 3

In a small bowl, stir together melted butter, oil, salt, and pepper. Gently loosen the skin on the chicken breast and thighs and rub the butter mixture under the skin and all over the outside of the chicken.

Step 4

Squeeze the lemon over the chicken, and place the rinds in the cavity along with the halved garlic and 3 thyme sprigs. Using kitchen twine, tie the legs together. Place the onion slices and the remaining 3 sprigs of thyme around the chicken in the bottom of the pan.

Step 5

Place the roasting pan in preheated oven and immediately reduce the temperature to 425°F. Bake until golden brown and a thermometer inserted in the thickest part registers 165°F, about 1 hour 15 minutes to 1 hour 30 minutes, basting with juices every 30 minutes. Let rest at room temperature for 15 minutes before carving. Serve with roasted onion and pan drippings.