Preheat the oven to 450 degrees F.
Remove the turkey from the refrigerator; let stand at room temperature for 30 minutes. Tuck the turkey wings under the body.
Place the butter, garlic, sage, rosemary, thyme, parsley and salt and pepper to taste in the bowl of a food processor. Blend until smooth.
Season the cavity of the turkey with salt and pepper, then stuff with the onion, lemon and assorted herbs. Tie the turkey legs together with kitchen twine.
Rub the herb butter all over the outside of the turkey and under the skin of the breast. Season to taste with salt and pepper.
Place the chicken broth in a medium saucepan on the stove and keep warm over low heat.
Place the turkey in a roasting pan and bake for 45 minutes. Reduce the oven temperature to 350 degrees F and continue roasting, basting the turkey every 30 minutes with the chicken broth, until the turkey is done. This will take approximately 3 hours and you'll know that the turkey is done when a meat thermometer inserted into the thickest part of the turkey thigh registers 165 degrees F.
If the turkey seems like it's getting overly browned during the cooking process, cover it with foil.
Remove the turkey from the oven and tent loosely with foil. Let the turkey rest for 25 minutes. Slice, then serve.