Bistek Ala Zambales

BISTEK
 ½ kilo beef sirloin (cut into 3 " strips)
 2 tablespoons soy sauce
 2 tablespoons calamansi juice
 1 teaspoon salt
 1 teaspoon pepper
 cooking oil
 1 big red onion (sliced thinly to make rings)
Marinate beef in soy sauce, calamansi, salt & pepper for 30 minutes.
In a pan, heat oil and stir-fry beef until cooked and tender. Set aside
Sauté onion rings in oil.
Serve beef in a platter topped with onion rings.