Pat the sirloin filet dry with paper towels
Season both sides with salt and pepper
Let the steak sit at room temperature for 20 to 30 minutes
Heat a heavy skillet over medium-high heat until very hot
Add a small amount of oil with a high smoke point
Place the steak in the skillet and do not move it
Sear for 2 to 4 minutes on the first side
Flip the steak and sear for 2 to 4 minutes on the other side
Add butter, garlic, and herbs if desired
Spoon the melted butter over the steak while it cooks
Check the internal temperature with a meat thermometer
Cook to 125°F for rare, 130°F for medium-rare, 140°F for medium
Remove the steak from the skillet
Rest the steak for 5 to 10 minutes before slicing
Slice against the grain and serve