You read that right. This shop (please note the two dots over the "Ä", to not mix it up with something else) collects unsold food from different places, and sells it for way cheaper. This means that you can find all kind of bakery, from strawberry cakes to sandwiches for half the price and still perfectly good !
Eating in Zürich is usually extremely expensive, but here you got a special spot in the old town to eat well and for really cheap ! Their choice is wide and everything is good, you can blindly go for it. Since it's in the old town, it's perfect for a small break during your visit.
The shop is a bit hidden, look for the blue and round "Äss Bar" sign. At noon streams of students empty the counter, be there early !