Combine the soy sauce, lemon, and pepper in a bowl. Add the beef and marinate for 30 to 60 minutes.

Remove the beef from the marinade and pat it dry. Reserve the leftover marinade for later.

Heat a pan over high heat with the cooking oil. Add the beef to the pan and saute for a few minutes until the beef becomes lightly browned. Remove extra cooking liquid when frying to allow the meat to sear; reserve juices for later. Transfer the meat to a clean plate.

Add the onions to the pan and cook for 5-6 minutes until softened. Add the garlic and cook for another 30-60 seconds or until fragrant, stirring frequently.

Return the beef to the pan. Pour in the marinade, cooking liquid, and water.

Allow the mixture to come to a boil. Stir, then reduce the heat to low. Cover the pan and simmer for 45 minutes, stirring occasionally.

Season with salt and pepper to your liking. Place additional onion rings on top of the mixture, and recover the pan. Cook for another 15 minutes or until the onions soften.

Serve over rice, if desired.