The queue is long but you don't have to join it. Just head inside and it's not too difficult to get a table. I was served very quickly. The pasteis de Belem tarts were warm, fresh from oven and most of all, they were delicious. It was the right texture, creamy and not too sweet. You can sprinkle some cinnamon powder on top of it for more flavour but it was already great by itself. The tart crust has many layers and they were really crispy. Nothing beats coffee and tarts after visiting the monastery. It's the best I've tasted so far and reasonably priced. If you're in Lisbon, you must try it.