How to Make It
Preheat the oven to 350°. In a heavy 14-inch skillet, combine the sugar, light corn syrup, water and vanilla bean and seeds and bring to a boil, stirring to dissolve the sugar. Cook over moderate heat without stirring, gently swirling the syrup in the skillet occasionally and washing down the side of the skillet with a wet pastry brush, until a medium-light amber caramel forms, about 10 minutes. Off the heat, stir in the butter. Add the sliced quince and cook over moderately low heat, stirring occasionally with a nonstick rubber spatula, until softened, about 5 minutes. Let the quince cool slightly. Evenly distribute the quince slices over the bottom of the skillet or, for a neater appearance, carefully arrange them in concentric circles.
On a lightly floured work surface, roll out the puff pastry to a 14-inch square. Using the skillet lid as a template, cut out a 14-inch round. Cut eight 1-inch-long steam vents in the pastry round and lay it over the fruit. Bake the tart in the center of the oven for about 55 minutes, until the pastry is golden brown and cooked through. Let the tart stand for 15 minutes.
Cover the tart with a large plate and very carefully invert the tart onto the plate. Cut into wedges and serve with crème fraîche.