In top down shots, we are directly above the food looking down onto it. This is great if you want to show a lot of things in the image at once.
The Diner's View would simply be at an angle as you were sitting looking at the food. That would be somewhere between 20 - 40 degrees.
For straight on view, the camera is almost parallel to the cake. These are great for dishes that you want to emphasize the height of the subject.