What is the Japanese rolled omelette often found in bento?

The Japanese rolled omelette often found in bento is tamagoyaki.

Tamagoyaki is made by cooking beaten eggs in several thin layers, rolling each layer over the previous one, and slicing the finished omelette into pieces. It is traditionally prepared in a rectangular pan called a makiyakinabe, which helps create its distinctive block-like shape. Recipes commonly include sugar, salt, soy sauce, and sometimes mirin or dashi.

The name combines tamago, meaning “egg,” with yaki, referring to cooking over direct heat. Related versions can taste quite different: dashimaki tamago contains more dashi and is softer and less sweet, while datemaki includes fish paste and is associated with New Year celebrations. Tamagoyaki is also served at breakfast and as a topping for sushi.

Its association with bento became especially strong as the dish grew popular with Japanese children in the mid-20th century. It is sometimes confused with onsen tamago, a gently cooked egg, or chawanmushi, a steamed savory custard; neither is a rolled omelette.