Preheat over to 350°. Cut the fennel bulbs into quarters, discard the stems. Cut the lemons into halves and cut the garlic bulb in half (no need to peel).
In a mixing bowl, combine 4 tablespoons (½ stick) of butter, the juice of 1 lemon and the leaves from 5 sprigs of thyme. Mix to combine.
Remove the turkey breast from packaging, discard bag of gravy if present. Pat dry with paper towels.
Season the inside and out generously with salt and pepper.
Stuff the cavity with the garlic, 1 bulb of fennel, 5 sprigs of rosemary, 1 lemon. Place the turkey in the roasting pan breast side up. Use the remaining fennel bulb quarters to prop the turkey up in place.
Pour the lemon butter mixture over the turkey. Cut the remaining butter into ¼ inch pads. Using your fingers or a pairing knife, loosely separate the skin from the breast meat. Slide in the pads of butter and remaining rosemary sprigs.
Pour in 1 cup of broth into the bottom of the roasting pan, loosely tent with foil and place on the lowest rack in oven.
Roast for 2 hours, basting every 30 minutes. Remove the foil and continue roasting until a thermometer inserted into the thickest part registers 165°
Transfer from the roasting pan to a large cutting board. Cover with foil for 20 minutes before carving.
If you plan to make pan gravy, hold on to the drippings in the roasting pan.
