Cutthe thin-sliced beef to bite sized pieces, cabbage, and onion to thin slices. Place the cabbage and onion in a microwave safe container and cover with a microwave safe wrap. Microwave for 1 minute.
Heat oil in a skillet and add in the yakisoba noodles. cook the noodles and add in small amounts of water to steam and loosen the noodles.
Pour in 1/2 of the yakisoba sauce and stir together. Using a spatula, push or slice the noodles to the center of the skillet.
Top the noodles with cabbage and onions, and place the beef around the noodles. Sprinkle on the rest of the yakisoba sauce over the beef and let the beef cook.
Add butter on top of the vegetable, sprinkle mayonnaise and aonori. To finish, sprinkle pepper. Before serving, stir all together and enjoy!