Grilling brings out a T-bone's natural succulent flavors without the help -- or the calories -- of a pool of oil and butter in a pan. This formidable steak is two prized cuts in one: the top loin and the tenderloin, also known as New York strip or fillet mignon. The whole T-bone is tender and juicy, but the tenderloin is better marbled and more flavorful. It also cooks faster than the rest of the steak, complicating cooking an entire T-bone to medium-rare. To remedy this, start with indirect heat and end with a high-heat sear to develop a nice crust to contrast the soft underlying meat.
Salt the T-bone steak thoroughly with coarse kosher salt at least 40 minutes before grilling it, but preferably further ahead -- up to two or three days. The coarse grains draw moisture out of the meat while seasoning it, and over time the meat reabsorbs its water content.
Clean the grill with a scraping tool, and grease it well with cooking oil. Preheat it to medium-high. You'll grill in two stages; first gently over lower, indirect heat, then searing over higher, direct heat. If you have coals, pile them to one side to create two heat zones. If you're using a gas grill, you'll use your grill's upper rack, when the time comes, for lower heat.
Finish seasoning the T-bone with black pepper and any other herbs or spices you want to use, such as dried rosemary or thyme, a little chipotle powder for spice, garlic powder or a favorite pre-made beef rub.
Place the T-bone steak on the cooler part of the grill, with the smaller tenderloin flap farther from the heat source since it cooks faster than the strip side. Close the lid. Flip the steak over once every minute or so to cook it evenly, rotating it as needed to keep the tenderloin section away from the heat.
Grill the T-bone until it registers 123 to 125 degrees Fahrenheit on an instant-read meat thermometer. This should take about 10 minutes, and allows you to finish the steak over high heat without overcooking it. When using a meat thermometer, insert it into the middle of the steak, taking care not to allow the stem to come into contact with bone or a section of fat.
Move the steak over to the hot zone of your grill. Sear each side for about 1 minute, until it becomes dark brown and crisped. An instant-read thermometer should read 130 to 135 F, medium-rare. This is quicker than searing at the start of cooking, since the meat is already well on its way.
Transfer the T-bone to a plate to rest for at least 5 minutes so it can finish cooking. Its internal juices also redistribute back into the muscle fibers, which keeps them from bleeding out when you slice the meat.