Preheat your oven to 400°F (200°C).

In a dry skillet over medium heat, toast the coriander seeds for about 2-3 minutes until fragrant. Remove from heat and let cool slightly, then crush them coarsely using a mortar and pestle or a spice grinder.

In a small bowl, mix together the crushed coriander, smoked paprika, salt, and pepper.

Rub the beef tenderloin with olive oil, ensuring it is evenly coated. Then, generously coat the beef with the spice mixture, pressing it onto the surface.

Heat a large oven-safe skillet over medium-high heat. Once hot, add the beef tenderloin and sear on all sides until nicely browned, about 2-3 minutes per side.

Transfer the skillet to the preheated oven and roast the beef for about 20-25 minutes, or until it reaches your desired level of doneness (130°F for medium-rare).

While the beef is roasting, prepare the black garlic compound butter. In a bowl, combine the softened butter, mashed black garlic, chopped parsley, and lemon juice. Mix until well combined. Set aside.

Once the beef is done cooking, remove it from the oven and let it rest for about 10 minutes before slicing.

Serve the sliced beef tenderloin topped with a dollop of black garlic compound butter.