Slice the onion into 1cm wedges. Dice the potatoes into small bite-sized pieces and soak in water to remove excess starch, then drain. Roughly chop the carrot into small bite-sized pieces.

In a microwave-safe bowl, mix the yakiniku sauce, water, and beef. Add the onion, potatoes, and carrot, and mix lightly.

Cover the bowl loosely with plastic wrap and microwave at 600W for about 10 minutes. Let it sit covered for another 5 minutes to steam.