To prepare the subject cake having uniformly foamed texture, palatability and meltability similar to those of a castella (a Japanese sponge cake) while keeping the surface gloss and springiness of a steamed bun by adding a bicarbonate and an acid (salt) under a specific condition to a cake dough composed of wheat flour, sugars, whole egg and milk.

A dough for a steamed bun composed mainly of wheat flour, sugars, egg and milk is mixed with one or more kinds of bicarbonates and the obtained mixture is quickly incorporated with one or more kinds of organic acid (salts) or inorganic acid salts to perform the reaction at a relatively early stage before starting the gelatinization of the starch in the dough in the steaming process. A stable whipped dough is easily producible by this process.