1. In a bowl, combine the flour, sugar, and salt. Add the cold butter and mix well. Add the cold water and form a dough. Refrigerate while you prepare the filling.
2. Next, in a small pan, melt the butter with the sugars and add the rum until it caramelizes. Finally, pour the caramel into a baking dish, arrange the sliced apples on top, and then place the dough over the apples.
3. Bake for 25 minutes or until the pastry is golden brown at 180 degrees Celsius (350°F). Remove from the oven and invert the tart onto a serving plate. Serve with whipped cream.
