Preheat your grill or a cast-iron skillet over medium-high heat.

In a small bowl, mix together the smoked paprika, salt, and black pepper. Rub this mixture all over the filet mignon steaks, ensuring they are evenly coated.

In the meantime, heat 1 tablespoon of olive oil in a skillet over medium heat. Add the sliced onion and cook, stirring occasionally, until the onions are charred and caramelized, about 10-12 minutes. Remove from heat and set aside.

In the same skillet or on the grill, add the remaining olive oil and sear the filet mignon steaks for about 4-5 minutes on each side for medium-rare, or until your desired doneness is reached. Use a meat thermometer to check for an internal temperature of 130°F (54°C) for medium-rare.

Once cooked, remove the steaks from the skillet or grill and let them rest for 5 minutes.

For the gravy, in the same skillet used for the steaks, add the beef broth and bring to a simmer, scraping up any browned bits from the bottom of the pan. Stir in the black truffle oil and butter, whisking until the gravy is smooth and velvety.

To serve, place the filet mignon steaks on a plate, top with the charred onions, and drizzle with the black truffle gravy. Garnish with chopped parsley.