Portugal dissolved its religious houses in 1834, and the monks at the Jerónimos monastery — who had long sold sweet pastries to bring money in — passed their recipe to a sugar refinery next door. In 1837 that business opened as the Antiga Confeitaria de Belém and has been making the same tart ever since. It is a cup of laminated pastry, shattering-thin, filled with egg custard baked so hot the top scorches into dark blisters. The recipe is held by a small number of pastry chefs and mixed in a locked room, which is why the shop is careful to call them pastéis de Belém: everywhere else in the world they are pastéis de nata.
The building runs back much further than the doorway suggests, through tiled room after tiled room seating hundreds. The queue outside looks worse than it is and is mostly for the takeaway counter. The tarts come out of the oven continuously and the correct way to eat them is immediately, still hot, with cinnamon and icing sugar from the shakers on the table and an espresso to cut the sugar. Cold, they are a different and much lesser object.