Pat the beef loin steak dry with paper towels
Season both sides with salt and black pepper
Let the steak sit at room temperature for 20 to 30 minutes
Heat a skillet or grill over medium-high to high heat
Add a small amount of oil to the pan if using a skillet
Place the steak on the hot surface
Cook without moving it for 3 to 5 minutes per side for medium-rare, depending on thickness
Flip once and cook the other side
Sear the edges briefly if needed
Check doneness with a meat thermometer
Remove at 125°F to 130°F for rare
Remove at 130°F to 135°F for medium-rare
Remove at 140°F to 145°F for medium
Transfer the steak to a plate or cutting board
Rest for 5 to 10 minutes
Slice against the grain
Serve immediately