Season steak with salt and pepper. Drizzle with oil. Heat a large frying pan over high heat (or fire up the barbie). Cook steak for 2-3 minutes each side for medium rare or until cooked to your liking. Transfer to a plate. Set aside for 5 minutes to rest. Thinly slice.
Slice baguette into rounds on an angle. Place rocket leaves on baguette slices. Top with steak and dollop with caramelized onion relish.