Remove the prime rib from the refrigerator and let it sit at room temperature for about 1 hour before cooking. Preheat your oven to 450°F (232°C).

In a small bowl, mix together the smoked sea salt, toasted fennel seeds, black pepper, garlic powder, and onion powder. Drizzle olive oil over the prime rib and rub it all over the roast, ensuring it is evenly coated. Generously apply the spice mixture to the surface of the prime rib, pressing it into the meat.

Place the prime rib on a rack in a roasting pan, bone side down. Roast in the preheated oven for 20 minutes to develop a crust. After 20 minutes, reduce the oven temperature to 325°F (163°C) and continue to roast until the internal temperature reaches your desired doneness (approximately 130°F (54°C) for medium-rare). Use a meat thermometer for accuracy, and keep in mind that the temperature will rise slightly as it rests.

Once done, remove the prime rib from the oven and cover it loosely with aluminum foil. Let it rest for at least 20-30 minutes before slicing to allow the juices to redistribute.

In a mixing bowl, combine the softened butter, mashed black garlic, fresh parsley, lemon juice, salt, and pepper. Mix until well combined and smooth. Transfer the butter mixture onto a piece of plastic wrap, shape it into a log, and refrigerate until firm.

Slice the rested prime rib and serve with slices of the black garlic confit butter on top, allowing it to melt into the warm meat.