Pat the sirloin dry with paper towels
Season both sides with salt and pepper
Let it sit at room temperature for 20 to 30 minutes
Heat a skillet or grill over medium-high heat
Add a small amount of oil to the skillet if using one
Place the sirloin in the hot pan or on the grill
Cook for 3 to 5 minutes per side for medium-rare, depending on thickness
Flip only once if possible
Use a meat thermometer to check doneness
Remove at 130 to 135 F for medium-rare
Remove at 140 to 145 F for medium
Rest the steak for 5 to 10 minutes
Slice against the grain
Serve immediately