A tenderloin fillet is a richly-flavored, often highly-marbled cut of meat that generally demands a high price in comparison to other cuts. The quality of the meat you choose will determine the texture and flavor of the meat, and meat labeled prime is the highest quality, followed by choice and select, and they are priced accordingly. Prime fillets can be slightly harder to find, but are worth seeking out for many.
Remove the beef tenderloin fillet from the refrigerator to warm to room temperature 90 minutes before cooking. Keep the tenderloin fillet covered with plastic wrap at all times.
Pat the steak dry with paper towels until no moisture remains, changing the paper towels as necessary.
Brush both sides of the meat with extra virgin olive oil or a 50:50 mixture of extra virgin olive oil and melted butter. Season both sides of the meat with sea salt or kosher salt and freshly ground black pepper to taste along with any fresh or dried herbs you want to use.
Heat a sauté pan large enough to hold the steak over high heat until just to the point of smoking.
Place the steak in the sauté pan. Cook the steak for two to three minutes on each side for rare steak, four to five minutes for medium and six to seven minutes for medium well. For more well-done steak, cook the meat for seven to nine minutes on both sides. Avoid moving the steak during the cooking process.
Transfer the steak to a serving platter or plate. Allow it to rest without slicing or cutting it for five to seven minutes so the juices can redistribute. Serve after a minimum of five minutes have passed.
Thinner cuts of meat will need slightly less time to cook and thicker pieces of meat will need a bit more. For best results, use an instant-read thermometer to check the doneness of the fillet. For rare steak, the internal temperature should be between 120 and 130 degrees Fahrenheit, medium should be between 140 and 150 and medium well should be between 150 and 160 degrees.
Most chefs will advise against cooking steak past the 160-degree mark, as the meat may become undesirably dry and less flavorful.