How do I perfectly prepare a sirloin steak……?

I’d like one cooked medium-rare and one medium, and I’m looking for that restaurant-quality taste and texture.

I can cook it on either a George Foreman grill (which I don’t really like to use because I always manage to overcook meat on that thing), or either a cast-iron skillet or a regular non-stick pan. What should I use to season them, how high heat should I use, and how long should I cook them?

The reason you overcook with a George Foreman is that it presses the meat–somthing that restaurants do when they want to cook a steak past medium. Given the choices listed, I would use the cast iron (Outback uses a flat grill for all their steaks). At my restaurant, we only use kosher salt and fresh ground pepper for steaks. Heat the skillet over high heat with nothing in it until blazing hot. Put in the steak and cook for about 1 to 1 1/4 minutes per side (MR or Med) then remove to a warm plate and cover loosely with aluminum foil for at least five minutes–this "resting" step is critical! It makes the difference between a steak that is seared on the outside and rare in the middle and one that is perfectly cooked all the way through. TIP: cooking times may vary, depending on how hot your burner is, thickness of the pan & steak, etc. Use the "poke test" to determine doneness. While your left hand is completely relaxed, poke the ball of your left hand (near the base of your thumb) with your right index finger. How much it gives is approximately the amount that a rare cooked steak will give when you poke it. Now touch your left index finger to your left thumb and poke again in the same place. Now it will be slightly firmer–this is medium rare. Your middle finger touching your thumb will be medium, and so on down the line. Now you don’t have to know the time (other than approximately), you just need to know the firmness of the cooked steak! Enjoy!