We want to have 7 pieces by only cutting our tasty cake with three straight and vertical cuts (maybe done with a katana :D),
I dont require to have all the pieces of the same size.
Sorry if it's repeated, but I couldnt find it here.
Very similar to another puzzle, but in this case we can not rely on the fact of making 3D cuts. All the cuts must be vertical.
THANKS TO @n00b, "Apparently there is a name for this type of puzzle; en.wikipedia.org/wiki/Lazy_caterer's_sequence"