- At least two hours before cooking, remove the steak from refrigerator and salt it liberally on both sides.
- When ready to cook, heat a heavy cast iron skillet over medium-high until the handle is very warm and a drop of water bounces in the pan. (Although cast iron is best because of its heat retention, any heavy-bottomed skillet will work. The pan should be large enough to hold the steak with enough extra space to get a basting spoon alongside the steak.) Depending on your cooktop, the size of the pan, and how you want your steak cooked, this might take five to 20 minutes.
- Pat the steak dry. When the pan is hot, place the steak on one of its edges in the pan. Cook for one minute, then rotate to another edge. Continue until the entire circumference of the steak is seared.
- Remove the pan from the burner and place the steak on a plate. Turn the heat to medium-low. Wait one minute, then add the butter and let it melt. Depending on the size of the pan, you may need more or less butter. You want enough to spoon up easily for basting.
- Return the steak to the pan, this time laying it on one side.
- Cook for one minute, basting the steak with the butter. Flip and cook for another minute, still basting. Repeat this five times, then check the temperature by inserting a probe or instant-read thermometer sideways into the steak at least two inches. You're looking for 120° F for medium-rare. It probably won't be there yet, so continue flipping and basting. You may have to do as many as ten or twelve flips.
- Remove the steak to a rack. Let rest ten minutes. Slice into 3/8-thick slices and serve. Top with cooked mushrooms and red wine sauce, if desired.
source: The Spruce