My latest favourite way to cook a steak:
Required:
Cast Iron Skillet
Oven - make sure you've got excellent ventilation as this has the potential to create a huge amount of smoke
Steak (Sirloin, Rib Eye, etc - approx 1.25-1.5" thick)
Salt
Fresh Ground Pepper
Garlic Powder
Onion Powder
Cayenne Powder (optional if you don't like spicy stuff)
Montreal Steak Spice
Get a cast iron skillet and place it in an oven, under maximum temperature from the broiler. Leave the skillet there for at least 15 minutes to soak up the heat, the longer the better. While this is warming up, you can season your steak, which should be completely thawed and close to room temperature. My personal suggestion is to mix some salt, fresh ground pepper, cayenne pepper powder, garlic powder, and onion powder in a mixing bowl and place the steak in there, pressing it down lightly on all sides to coat it. I also use Montreal Steak Spice in my rub, if you have any available in your area, pick some up and add it in to the mix. Rub the seasoning onto the steak to form a light coating, any excess should be rubbed off.
With an oven mitt, remove the skillet from the oven, and put it directly onto a pre-heated burner on maximum. Turn your oven temperature down to 400. Drizzle olive oil into the skillet and it should immediately begin to get very viscous and be easy to swish around, to coat the whole cooking surface in oil. Place the steak down and let it sear for 2 minutes without touching it. With a pair of tongs, flip the steak over, and with your oven mitts, put the skillet back in the oven. The flipped side should have a nice browned colour to it, but not black, and will have formed a nice crust. It shouldn't take more than about 5-6 minutes to get your steak to medium rare in the oven now and you can check it by touching the steak to feel for doneness. Be sure to use your oven mitts always when handling the hot skillet or you'll be on the receiving end of a harsh sear too!
Grilling: Determine the doneness of a steak
It is very important that once you've acheived your doneness, you take the steak off, put it on a clean plate, and tent it with some aluminium foil for 5-6 minutes, to let the meat relax and get all nice and juicy.
Be sure not to use any soap or detergents when washing your cast iron skillet off or you'll remove the seasoning that makes it naturally non-stick.