Preheat your oven to 425°F (220°C) and line a large baking sheet with parchment paper.

Place the whole chicken breast-side down on a sturdy cutting board and cut along each side of the spine to remove it.

Turn the chicken over, season it generously inside with salt and black pepper, and flatten it by pressing down on the breastbone.

In a mixing bowl, combine softened butter, olive oil, parsley, garlic, lemon zest, lemon juice, salt, and pepper to make the flavored butter.

Spread the flavored butter mixture under the skin and over the surface of the chicken.

Roast the chicken in the oven for 40-45 minutes, until golden brown and internal temperature reaches 165°F (74°C).

Remove from the oven and let the chicken rest for 10 minutes before serving.