Paper Wrapped Cake

Paper wrapped cake (Chinese: 紙包蛋糕; Jyutping: zi2 baau1 daan6 gou1) is a type of Chinese cake. It is one of the most common pastries served in Hong Kong. It can also be found in most Chinatown bakery shops. In essence, it is a chiffon cake baked in a paper cup.
In the bakeries of Chinatown, San Francisco, it is commonly referred to as "sponge cake."