Thaw your turkey: allow one day of thawing per 5lb in the fridge on a pan. Remove giblets and neck. Drain liquid, rinse, and pat dry with paper towels.
Place the turkey on a rack in a roasting pan. Sprinkle the inside and outside generously with salt and pepper.
Make the herb butter: In a bowl, combine butter, olive oil, lemon juice, herbs (parsley, sage, rosemary, thyme), minced garlic, salt, and pepper. Mix until well combined.
Carefully separate the skin from the breast and rub 1/4 of the herb butter under the skin. Rub the remaining butter all over the skin, breast, legs, and wings. Tuck wings under to prevent burning.
Stuff the turkey with the quartered onion and lemon. Tie the legs together with kitchen twine. If prepping ahead, refrigerate at this point.
If time allows, let the turkey sit at room temperature for an hour before cooking. Preheat oven to 425°F. Adjust oven rack so the turkey sits in the center.
Cook for 30 minutes at 425°F until the skin is crispy and golden. Reduce heat to 350°F. Tent loosely with foil. Bake for 13 minutes per pound at 350°F, or until the thickest part of the thigh reaches 165°F. Baste frequently with pan liquids.
Remove from oven and let the turkey rest, loosely covered with foil, for one hour before slicing. This allows the juices to redistribute for a tender, moist bird.