After three minutes on the second side, take the internal temperature of the sirloin steak. It should get to 135 degrees for medium-rare to rare. It’s important to make sure the sensor is fully in the center of the meat. Some analog dial-style instant read thermometers’ sensors are actually about 1 inch from the tip of the probe. Look at the shaft of the probe, and if there is a little super tiny circular indentation about 1 inch up, that’s the sensor! If yours doesn’t have that, the sensor is in the end of the shaft. For a steak like this, I like to pick it up with the tongs, then slide the thermometer into the steak horizontally so I am sure I reach the center of the steak with the sensor, and it isn’t going past the center and reading the temp on the other side!