In a large, shallow bowl, whisk together the soy sauce, calamansi (or other citrus) juice, black pepper, and minced garlic.
¼ cup Soy sauce, ¼ cup Calamansi juice, 1 teaspoon Black pepper, 4 cloves Garlic
Pound the beef flat with a meat mallet. Then thinly slice the beef, and place the slices in the marinade and turn to coat. Lest rest for 15-30 minutes, up to 2 hours.
1 lb Beef sirloin
While the meat is marinating, slice the onions thinly. Heat the oil in a pan over medium-low heat, then add the onions and saute until translucent and slightly browned, about 10-15 minutes. Remove and set aside.
1 small Onion, 2 Tablespoons Vegetable oil
In the same pan, add in the marinated beef. Cook until golden brown, about 2-3 minutes per side. Cook in batches to avoid overcrowding the pan.
Combine the onions and beef in the pan, then stir to combine and heat through, another 1-2 minutes.
Serve over steamed rice and enjoy!
Video
Notes
Add vegetables such as potatoes, carrots, or bell peppers for some extra bulk.
Simmer the marinade and use it as a sauce! Just make sure you heat it to boiling and let it simmer for at least 5 minutes to ensure it's safe.
You can also add the marinade to the pan with the beef and cover it, then let it simmer for as long as 30 minutes.
I highly recommend serving bistek with simple steamed rice.
The best substitute for Calamansi juice is Meyer lemon juice. If you can't find Meyer lemons, any citrus juice such as lemon, orange, or lime will work, as well as a blend of all three.