- With the rack in the middle position, preheat the oven to 425°F (220°C).
- On a non-stick baking sheet, or a baking sheet lined with a silicone mat, toss the potatoes with half of the oil. Season with salt and pepper. Roast for 15 minutes or until staring to brown. Add the asparagus, bell peppers and remaining oil. Mix well. Bake for 10 more minutes.
- Meanwhile, in a large ovenproof skillet over medium-high heat, brown the meat on both sides in 2 tbsp (30 ml) of the oil for 6 minutes for rare or until the desired doneness. Season with salt and pepper. Set aside on a plate.
- In the same skillet over medium heat, brown the onions in the remaining oil. Deglaze with the vinegar and let reduce until almost dry. Add the brown sugar and broth. Let reduce by half. Generously season with pepper.
- Return the meat to the skillet. Top with the cheese. Bake for 2 minutes or until the cheese has melted slightly. Serve the steak with the roasted vegetables and onion sauce.