In a small saucepan, combine the lemon juice, chopped rosemary and thyme, lemon zest and 1 stick butter. Cook until the butter is melted. Cut the remaining stick of butter into cubes and set aside. Place the turkey on a v-shaped rack in a large roasting pan. Pat the turkey thoroughly dry, and then brush the melted butter mixture all over. Liberally sprinkle with salt and pepper on both the outside and inside of the cavity. Fill the cavity with the cubed butter, sage, rosemary, thyme, garlic and onions. Tie the legs of the turkey together with string and tuck the wings underneath. Roast the turkey until an instant-read meat thermometer inserted into the thickest part of the thigh registers 165 to 170 degrees F and the juices run clear, about 2 1/2 hours. Remove from the oven and transfer to a cutting board or platter. Tent the turkey with foil and let stand 20 minutes before carving.
You could also purchase a pre-brined turkey. Preheat the oven to 350 degrees F.