Pat the filet mignon dry with paper towels
Season both sides generously with salt and black 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 high-smoke-point oil to the pan
Place the steak in the pan 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 second side
Sear the edges briefly if needed
Add butter, garlic, and herbs to the pan if desired
Spoon the melted butter over the steak while it finishes cooking
Check the internal temperature with a meat thermometer
Remove the steak at 125°F for rare, 130°F for medium-rare, or 140°F for medium
Transfer the steak to a plate or cutting board
Let it rest for 5 to 10 minutes
Slice and serve