In a non-reactive bowl, combine soy sauce, calamansi juice, garlic, sugar, salt, and pepper. Stir until sugar and salt are dissolved.

Add beef and massage to fully coat with marinade. Keep overnight in the refrigerator to cure. Drain meat from marinade.

Preheat grill on high

Add beef in a single layer and cook, turning on sides, for about 3 to 5 minutes or until liquid (meat will dispel liquid) is almost absorbed.

Cut into serving portions. Serve hot with vinegar, onion and fish sauce dipping sauce.