Its not a real cake, its glass actually....
Yep, looks like glass to me too.
there were a couple posts about this yesterday I think, where the link to this was posted, but I can't find it now.
However I would think to recreate the shape would be simple, to get that shiny look either fondant that is painted/airbrushed with pearl lustre dust.
OR a kind of poured RI which you would get a somewhat glassy look, and definitely the high gloss? Let us know if you do it and how!
It is glass, by Sweet and Shiny in Brooklyn, NY.
You could get a similar effect with blown sugar, but that would take some pretty solid skills.