In a deep skillet, heat the oil to around 350.Cut the tortillas into wedges! Cook the onion and tortilla until the tortilla is crisp and golden brown. Remove from the Skillet and drain on a paper towel.Drain the skillet of oil and leave the tid-bits in the skillet.
Over medium heat, cut the beef into cubes and add the beef in the skillet, heat for a short time 3-4 minutes. Add the tortillas and eggs. Season with salt and pepper. Cook stirring constantly until eggs are firm.Stir in the tomato sauce, reduce heat to low or simmer until thickened, about 5 to 7 minutes.
Top with cheese, cook until cheese melts and serve.