2. In a sealable container, combine balsamic vinegar, garlic, rosemary, olive oil, and black pepper. Mix.
3. Put steak fillet in marinade, cover with lid, and shake to coat it well. Place the container in refrigerator for at least 4 hours or overnight.
4. Remove the streak from refrigerator, at least one hour before, so that it comes to room temperature.
5. Wipe excess marinade from steak, put them on grill and cook until medium rare.
6. Serve steak with cabernet sauce, and green salad.