We call this a bad cake, and the homophony varies from place to place. I think it should be the same thing, that is, a cake steamed from a mold, round like an egg tart, with black skin and yellow inside. Compared with ordinary cakes, the crust is darker, like the color of mahogany, and the inside is golden and soft. The outer skin is slightly harder than the inner layer and can be preserved for a long time. According to the current standards, the trough cake is a relatively low-grade snack, but in the past, it was the spiritual pillar of poor children for the New Year. Visiting relatives and friends and bringing a box of cakes during the Spring Festival will make the host family very happy. I once read a novel saying that it was a very poor family. When the old lady died, she was looking forward to eating a cake, which was enough to show the preciousness of the cake at that time.