Caramelized Onion and Gorgonzola Quiche

On a lightly floured work surface, roll out the dough to 1/4 inch thick. Press the dough onto the bottom and up the sides of an 8 × 11-inch rectangular tart pan with a removable bottom; trim the dough flush with the top edge of the pan. Prick the bottom all over with a fork. Transfer to a large rimmed baking sheet. Freeze until firm, about 30 minutes. Preheat the oven to 400°F.

Line the tart shell with parchment paper, and fill with pie weights or dried beans. Bake until the dough starts to feel firm on the edges, about 20 minutes. Remove the parchment and weights; continue baking until the crust is pale golden brown, about 10 minutes. Let cool completely on a wire rack. Leave the oven on.

Heat the oil in a large, heavy-bottomed skillet over low heat until hot but not smoking. Cook the onions, stirring frequently, until golden brown, about 30 minutes. Let cool.