1. Pound the steaks to flatten them.
2. Use a bowl large enough to hold the steaks, and mix in it the vinegar and olive oil.
3. Push garlic through a press into the mixture, and add the rosemary.
4. Mix well, then place steaks in the mixture and turn them until coated.
5. Steaks can be grilled or pan-fried.
6. If you grill them, cook over brisk heat for 2 or three minutes on a side and keep basting with the marinade throughout.
7. To panfry, place steaks and marinade in a very hot skillet and cook for three to four minutes on a side.
8. Turn steaks twice and spoon marinade over each time.
9. Sprinkle with salt and pepper to taste.
10. Serve topped with lemon slices.