An adjective, meaning something is of excellent quality, soft and moist with a creamy centre

Originally from Family Guy, from the episode in which Mort Goldman said,"The kids were very mean to me in high-school. They used to call me tastycakes and shove pinecones in my ass."(As seen in Little Nicky)

Tastycakes is an adjective. It describes someone's ass. As if, it were tasty... As tasty as cake.