Alsatian Tart with Leeks, Fromage Blanc, and Bacon

Heat the olive oil in a skillet over medium heat. Add the onion and season with salt. Cook until softened but not colored, about 8 minutes. Let cool.

Put the bacon in a skillet over medium heat. Cook, stirring, until it renders some of its fat and just begins to crisp, about 5 minutes. Transfer it to a small bowl with a slotted spoon.

On a lightly floured surface, roll the puff pastry into a 12-inch circle (if the packaged pastry is round) or into a 10 by 12-inch rectangle (if the packaged pastry is rectangular). Transfer it to a baking sheet and prick with a fork in several places. Return it to the refrigerator for 30 minutes.