Steak Eat offers a method for cooking sirloin steak in the oven by baking it. It includes bringing the steak to room temperature, seasoning it with salt, baking it in a preheated oven, letting the steak rest for a few minutes, then returning the steak to the oven to brown.
Start with a thick 1 to 2-inch-thick sirloin stake. Remove the steak from refrigeration and allow it to rest at room temperature for about 40 minutes to help the finished steak turn out juicier and more tender. Season the steak with kosher salt but not pepper, as the pepper may burn while baking. Preheat the oven to 285 degrees Fahrenheit, or 250 degrees Fahrenheit if using an oven fan.
Cover a pan with tinfoil to create a dripping tray. Set the steak on a grill rack, place it in the oven and set the drip tray directly beneath. Shut the oven door and set a timer for 25 minutes. Use a thermometer to check the steak's internal temperature, and remove the steak when it is just below the desired level of doneness.
Let the steak rest for about 10 minutes while heating the oven to the maximum temperature setting. Set the steak back on the rack and bake for 10 more minutes to brown. Remove the steak to a plate, cover with tin foil and allow to rest. Season with freshly ground black pepper about five minutes before cutting to serve.