Place the beef slices between two sheets of plastic wrap or wax paper. Gently pound the beef with a meat mallet until it’s thin and tender. Be careful not to overdo it to avoid tearing the meat.

In a bowl, combine the tenderized beef, soy sauce, calamansi juice, minced garlic, and ground black pepper. Mix well and let it marinate for at least 30 minutes, or for better flavor, refrigerate for 1-2 hours.

Heat a bit of oil in a large pan over medium heat. Add the onion rings and sauté until they become soft and slightly caramelized. Remove from the pan and set aside.

Using the same pan, add more oil if necessary and heat it over medium-high heat. Fry the marinated beef in batches, making sure not to overcrowd the pan. Since the beef is tenderized, it will cook quickly, about 1-2 minutes per side. Remove the beef from the pan and set aside.

In the same pan, add 2 tbsp of cooking oil. Sauté the minced garlic and minced onion until they become fragrant and slightly translucent.

Add the marinated beef to the pan, searing it for 1-2 minutes on each side, until browned.

Pour in the marinade you set aside earlier. Let the beef simmer in the marinade for a few minutes until the sauce thickens and the beef is cooked through.

Add the glazed onion rings to the pan, letting them warm through in the sauce. Taste the sauce, and add salt if needed.

Transfer the Bistek Tagalog to a serving dish, garnishing it with the glazed onion rings. Enjoy with steamed rice!