The Onion King is the ruler of the Onion Kingdom. He rules alongside his dog Kevin and can understand his speech, which he will occasionally translate for the player.
In Overcooked! 2 he accidentally summons the Unbread by reciting a recipe from the Necronomnomicon. In order to stop the ravenous hoard, he sends the player on a quest to collect a series of recipes and thereby become better, more cooperative cooks.