Marinate the meat in lemon juice, soy sauce, pepper and salt for 3 hours or more. Cook onion rings in oil until transparent. Transfer to serving dish, leaving the oil on the skillet. Add the meat to the skillet and cook over high heat, stirring often, until tender. Transfer the meat to a serving dish. Add marinade and water to the skillet, simmer for 10 minutes and pour over the meat and onion rings.
Makes approximately 4 servings.