Remove the neck and giblets from the turkey’s cavity. Rinse the turkey under cold water, then pat it dry with paper towels.

Using poultry shears, cut along both sides of the backbone to flatten the turkey. Break the breastbone to ensure the turkey lays flat.

Preheat your oven to 425°F (220°C) and position an oven rack in the lower third.

In a roasting pan, scatter sliced onions, minced garlic, and fresh parsley to create a base. Pour water over the vegetables.

In a mixing bowl, combine softened butter, light olive oil, lemon zest, lemon juice, minced garlic, chopped parsley, sea salt, and black pepper.

Season the inside cavity of the spatchcocked turkey with salt and pepper and place it on top of the vegetable bed.

Slide the flavored butter mixture under the skin of the turkey and massage it to distribute evenly. Brush remaining butter over the skin.

Bake the turkey at 425°F (220°C) for 30 minutes, then reduce to 400°F (200°C) and continue roasting until the internal temperature reaches 165°F (74°C), about 1 hour.

Remove the turkey from the oven and tent loosely with aluminum foil. Allow to rest for 30 minutes before carving.