
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.
In a wide pan over medium heat, heat about 1 tablespoon oil.
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.
Add another 1 tablespoon of oil and continue to cook until the meat is lightly browned and caramelized.
Remove from pan and cut into serving portions. Serve hot.