There are several Vapianos in Budapest - at least one in the city center, one in Westend shopping mall and one in Mom Park shopping mall. The concept is based on self-service - you get a credit card type of card, go to the food stalls, choose what you want to eat and drink and show your card.
The variety is actually pretty good, not only pizza and pasta as I first thought. Everything is prepared when you make the order so there's nothing standing there for hours. My favorite is - surprise, surprise - Caesar salad with or without chicken, both goes. The portion is not too small not too huge and the ingredients are fresh and you can see while they prepare it.
When you are leaving the place you go to the cashier at the entrance, show the given card and pay what it shows.
Easy and fast - well, not so fast if you're there at lunch time... but easy anyway.