Step 1: Prepare the Turkey

1. Preheat the oven to 220°C (425°F).
2. Remove the giblets from the turkey cavity and pat the turkey dry with paper towels.

Step 2: Make the Herb Butter

1. In a bowl, combine softened butter, minced garlic, lemon zest, parsley leaves, sea salt, and black pepper. Mix well.

Step 3: Stuff and Butter the Turkey

1. Gently loosen the turkey’s skin over the breast by sliding your hand underneath it, taking care not to tear it.
2. Spread half of the herb butter under the loosened skin. Rub the remaining butter over the outside of the bird.
3. Stuff the cavity with the halved lemon, garlic head, bay leaves, and onions for aromatic flavor.

Step 4: Add Bacon and Lemon

1. Arrange the smoked streaky bacon rashers over the turkey breast in a criss-cross pattern.
2. Drizzle olive oil over the bacon and squeeze the juice of two lemons over the turkey.

Step 5: Roast the Turkey

1. Place the turkey in a large roasting pan and loosely cover it with aluminum foil.
2. Roast at 220°C (425°F) for 30 minutes. Reduce the oven temperature to 180°C (350°F) and continue roasting, basting with pan juices every 30 minutes.

Step 6: Check for Doneness

1. Roast the turkey for approximately 2 ½ to 3 hours, or until the internal temperature in the thickest part of the thigh reaches 75°C (165°F).
2. If the bacon darkens too quickly, cover the breast loosely with foil.

Step 7: Rest and Serve

1. Remove the turkey from the oven and transfer it to a serving platter.
2. Cover the bird with foil and let it rest for at least 30 minutes before carving.