Kasutera is a traditional sponge cake made with sugar, flour, eggs, and starchy syrup. This Nagasaki specialty is raised solely by egg foam, with no added butter or oil, and has a soft, moist, and spongy texture. The cake is also known as Castella, and was brought to Japan in the 16th century by Portuguese merchants.
Its name is derived from pao de Castela, meaning bread from Castille. Today, it is common to find Nagasaki kasutera in many variations, with flavors such as chocolate, green matcha tea, brown sugar, or honey. It is a popular gift and a nice souvenir to give to friends or relatives.