Preheat the oven: Preheat to 350°F (175°C).
Prepare lemon butter: In a bowl, mix the butter and lemon zest until well combined.
Loosen turkey skin: Gently loosen the skin of the turkey by sliding your fingers under the skin, starting from the neck and working your way down, being careful not to tear the skin.
Spread lemon butter: Spread the lemon butter mixture under the turkey skin, pushing it as far as possible. Smooth the skin back into place.
Season the turkey: Season the cavity with kosher salt and place the halved lemon and onions inside. If desired, truss or tie the legs of the turkey for even cooking. (See notes for more direction on trussing.)
Prepare garlic herb paste: In a small bowl, mix the crushed garlic, chopped rosemary, and olive oil to make a paste. Rub this mixture over the skin of the turkey, coating it evenly. Sprinkle generously with flaky sea salt.
Prepare the roasting pan: If your roasting pan lacks a rack, place slices of onion at the bottom to act as a trivet. This ensures that the turkey roasts evenly and doesn't stick to the bottom of the pan.
Place the turkey in the pan: Place the prepared turkey in the roasting pan, either on the rack or on the onions.
Add wine and cover: Pour the dry white wine (or chicken broth) into the bottom of the roasting pan. Cover both the turkey and the pan completely with foil, creating a tent to trap steam and help the turkey stay moist.
Roast the turkey: Cook in the preheated oven for about 15 minutes per pound of turkey (approximately 1 hour 45 minutes for a 7-pound turkey). For larger birds, ensure the total cooking time aligns with this rule (e.g., a 12-pound turkey would cook for about 3 hours).
Crisp the skin: After the initial cooking time, remove the foil and increase the oven temperature to 425°F (220°C). Return the turkey to the oven for an additional 30 minutes, or until the skin is golden brown and crispy.
Check for doneness: Insert a meat thermometer into the thickest part of the turkey (between the breast and thigh). The temperature should read 165°F (75°C). Alternatively, pierce the thigh with a skewer—if the juices run clear, the turkey is done. If they are pink, continue cooking and check again in 10-minute intervals.
Rest the turkey: Once cooked, remove the turkey from the oven, loosely cover with foil, and let it rest for at least 30 minutes and up to an hour before carving. This resting period allows the juices to redistribute, ensuring a moist turkey.