In the bowl of a food processor combine the flour, butter, and salt until the mixture resembles breadcrumbs. Add the ice water, a little at at time, and process until the mixture forms a ball. Wrap it in plastic and refrigerate. Preheat the oven to 350F. Peel and core the apples. Cut them into quarters and rub them with lemon juice to prevent browning. Place the sugar in a 10-inch cake pan and cook it over a low heat until it caramelizes, shaking the pan from time to time. Remove the pan from the heat and add the vanilla to the caramel. Place the apple quarters on top of the caramel, rounded-side down. Cover with aluminum foil and bake for 1 hour. Cool the tart, then chill overnight. The next day, Preheat the oven to 350F, roll out the dough on a lightly floured surface to a 1/4-inch thickness. Remove the foil from the cake pan. Place the crust over the apples. Bake for 40 minutes. Cool on a rack. Half an hour before serving, heat the cake pan over high heat on top of the stove, until it boils. Remove from the heat and invert it onto a serving platter. Serve warm with orange-flavored custard sauce.
