Mix the soy sauce, nuoc mam, ginger, garlic, and pepper, add the beef cubes, mix well. Marinate this in a large bowl for at least one hour up to over night.
Heat the peanut and sesame oil in a large wok or sauté pan on medium high. Drain beef cubes reserving the juice. Toss beef in flour then fry them in the heated oil. Stir briskly for 3 to 4 minutes or until cooked. Remove them from pan and reserve them in a warm oven so they stay hot.
For the rice: use the same wok to scramble the beaten eggs. Add soy sauce, reserved marinade, five-spice powder, and sesame oil. Cook for about one minute. Add the cooked rice bit by bit, and then add tomato sauce. Stir well and cook 4 minutes. Add extra salt and pepper if desired.
Mix lemon sauce ingredients together and pour equal amounts into small dipping cups, one for each person.
Serve the beef pieces with the rice, lemon sauce, and chopped raw onion.