Cut the onion into bite-sized pieces after halving it vertically.

Slice the scallops horizontally into halves.

Mix the oyster sauce, mayonnaise, and sake in a bowl to make the sauce.

Heat salad oil in a frying pan over medium heat, add the onion, and stir-fry until softened. Push the onion to the side.

Add the scallops to the empty space in the pan and sear both sides until their color changes.

Pour the sauce into the pan and stir-fry everything together until evenly coated.