To cook a top sirloin steak, the best approach involves seasoning, searing, and finishing it to your desired doneness using either the oven or a grill. Here is a straightforward method:

1. Preparation : Take the steaks out of the refrigerator and let them rest at room temperature for about 30 minutes. Pat them dry and season generously with kosher salt and freshly ground black pepper.
2. Searing : Heat a high-smoke-point oil (such as olive, avocado, or canola oil) in a hot cast iron skillet over medium-high heat. When the oil shimmers but does not smoke, place the steak in the skillet. Cook undisturbed for 2-3 minutes until browned. Flip and sear the other side for another 2 minutes.
3. Cooking to Doneness : After searing, transfer the skillet with the steak to a preheated oven at 425°F (about 220°C). Roast the steak until it reaches your preferred internal temperature—about 130-135°F for medium-rare, or 140-145°F for medium. This usually takes around 5-10 minutes depending on thickness.
4. Resting and Serving : Remove the steak from the oven and let it rest for 5 minutes to allow juices to redistribute. During resting, spoon the pan juices or melted butter over the steak for extra flavor.

Alternatively, grilling top sirloin steak can be done using a two-zone fire method—searing on the hot side for a few minutes and finishing on the cooler side until the desired temperature is reached, followed by a rest with butter on top for juiciness. This method yields a juicy, flavorful, and tender top sirloin steak ready to be sliced against the grain and served.