Begin by preheating your oven to 325° F.
While it is in the roasting pan, open the package of your thawed turkey. There will be lots of juice, so make sure to catch it all in the pan.
Drain the pan in a sink and take out the neck and any giblet bag from inside the turkey. Also take this time to search for any feathers that may have gotten overlooked. Let sit on the counter for 30 minutes to dry out the skin a bit.
Pat down your turkey with a paper towel.
In your roasting pan, place the carrots and celery at the bottom. These will be used for your gravy later.
Place the turkey in your roasting pan, and tuck the wings underneath the body.
*MAKE SURE TO TAKE OFF ANY RINGS OR JEWELRY FOR THE NEXT STEP*
Use your fingers to gently reach underneath skin and separate it from the meat. Be careful not to tear it.
Take half of your compound butter and put it underneath the skin. Take the other half and spread it all over the top of your turkey, trying to get as much of it coated as possible.
Next, stuff the turkey cavity with your lemons, onions, thyme, sage, and rosemary. I like to also place a couple pieces of onion to put in the pan around the turkey.
Put the turkey in the oven with the lid on or tented with tin foil.
After 2 ½ hours, uncover the turkey and raise the heat to 375° F.
Bake for another 1 ½ hours until turkey is fully cooked through and a nice golden brown on the outside. It may start getting brown earlier than the inside is done, in which case just place your lid or tenting foil back on.
At about the 3 hour and 15 minute point, start temping your bird in multiple places to see where it's at (you want it to be 165° F). All ovens cook differently and if yours happens to run hotter (or colder), the turkey could be done faster (or slower).
Let turkey rest on the counter for 30 minutes after cooking to let all the juices redistribute. Then it's carving time!