Preheat your oven to 375 degrees Fahrenheit.
While the oven is preheating, heat a tablespoon of oil in a skillet over high heat.
Season the steak with salt and pepper, and sear it in the skillet until browned on both sides.
Add sliced onions to the skillet and sauté until caramelized.
Once the steak and onions are ready, transfer them to a roasting tray. Make sure to scrape any leftover oil into the tray as well.
Roast the steak in the preheated oven for about 35-40 minutes, depending on how well-done you like your steak.
Once the steak is cooked to your liking, remove it from the oven and let it rest for a few minutes. During this time, you can spread your choice of sauce on the steak.
After allowing the steak to rest, slice against the grain and serve with your preferred sides.