I just purchased my first sponge birthday cake for my dove pan. It looks just fine but I'm wondering the use of the cavity in bottom. There is round cut area which can be pressed in. It's about 2½" by diameter and 2" deep. I suppose it's for small birthday gift or something you can lift from the pan after removing the cake. Or hiding a music box? Have you used that area somehow and have you cut the sponge off to get easier access? Perhaps even cut it larger.