Spread the sugar over the prepared base. In the centre of an oven preheated to 220°C, caramelize the sugar for approx. 7 mins. until light brown. Remove from the oven, scatter the butter on top of the caramel. Place the apples in the caramel, cut side down and overlapping slightly.
Approx. 20 mins. in the centre of an oven preheated to 220°C, remove.
Prick the pastry firmly with a fork and place loosely over the apples. Make a rim between the apples and the edge of the tin.
Bake for approx. 15 mins. Remove from the oven, leave to stand for approx. 2 mins., tip out carefully onto a cake plate, remove the baking paper, serve warm or cold.