1. Pound the steaks on both sides, using a mallet, until 1/4-inch thin. Season with garlic, lime juice, salt and pepper, and allow to marinate at least 1 hour, refrigerated.
2. Remove the steaks from the marinade and pat dry. In a large frying pan, heat the oil over medium heat until very hot, and brown each steak for 2-3 minutes on each side. Transfer the steaks to a serving platter and keep warm.
3. Add the marinade and onion to the pan and cook over medium-high heat until the onion is slightly wilted, 3-4 minutes. Garnish the steaks with the onion and parsley and serve immediately.