Mix 900g of thinly sliced beef sirloin with ¼ cup of lemon juice, ¼ cup of soy sauce, 1 sliced onion, 1 head of minced garlic, and ¼ teaspoon of ground black pepper. Marinate for about 30 minutes.
Lift out the beef and strain the marinade, keeping the liquid and the onion and garlic separately.
Heat 3 tablespoons of canola oil in a wide pan. Sear the beef in batches until browned and set aside. Sauté the onion and garlic from the marinade in the same pan until softened.
Return the beef and its juices, then add the marinade liquid and 1 cup of water. Bring to a boil, cover, and simmer for 40-50 minutes, until the beef is tender and the sauce reduced. Season with salt.
Top with 1 onion, sliced into rings. Turn off the heat and cover until the rings soften in the steam.
