Preheat your oven to 400°F (200°C).

In a mixing bowl, combine the softened butter, minced garlic, lemon juice, and lemon zest. Mix until well combined and set aside. Carefully cut the bone marrow lengthwise to expose the marrow and place the halves on a baking sheet.

Roast the bone marrow in the preheated oven for about 15-20 minutes, or until soft and bubbling. Remove and let it cool slightly.

Season the beef tenderloin generously with salt and pepper. In a large skillet, heat olive oil over medium-high heat. Sear the tenderloin on all sides until well browned, about 3-4 minutes per side.

In the same skillet, add chopped scallions and sauté for about 2-3 minutes until charred and fragrant. Remove from heat.

Remove the tenderloin from the skillet, place it on a cutting board, and press the sautéed scallions and chopped coriander onto the top to adhere.

Return the beef tenderloin to the oven and roast for an additional 15-20 minutes, or until it reaches your desired doneness (135°F/57°C for medium-rare).

Once cool enough to handle, scoop the marrow from the bones and mix it into the prepared butter until combined.

Let the beef tenderloin rest for about 10 minutes before slicing. Serve slices topped with the roasted bone marrow butter.