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A cast-iron skillet is great at conducting heat, meaning that it spreads it out evenly over the entire surface. Use a nice neutral oil to cook the steak in. Olive oil is great for pasta and eggplant, but not so great for cooking steaks. Canola or another vegetable oil is probably better.  For best results, use a thermometer to check the internal temperature of the steak. Here's a guide of how internal temperature corresponds to doneness:  120° F (48.8° C) = Rare 130° F (54.4° C) = Medium rare 140° F (60° C) = Medium 150° F (65.5° C) = Medium well 160° F (71.1° C) = Well done Aromatics you may use while pan-searing may include:  Rosemary Thyme Marjoram Garlic Sage As you cook your meat, the juices travel to the inside of your meat as the muscle fibers contract. If you cut your steak right after you take it from the grill, the juices in the center fall out more freely. If you wait for at least five minutes, the muscle fibers relax and the juices spread out more evenly throughout the whole steak. Enjoy your wonderfully cooked steak alongside some German potato salad and brussel sprouts, for example.

Summary:
Heat 2 tablespoons of oil in a cast-iron skillet over high heat until heavily smoking. Add the steak to the pan, paying attention to placement if pan has raised ridges. Flip frequently, about every minute or so, for about 6 to 12 minutes, until desired internal temperature has been reached. Before doneness has been reached, add 2 tablespoons of butter and any additional aromatics. After steak is cooked (steak will continue to cook off the heat), allow it to rest for at least five minutes. Enjoy.