Preheat the oven to 200°C/Fan 180°C/Gas 6.
Pastry first. On a floured board, roll out a disc of pastry that’s about 4mm thick. If using ready-rolled, simply unroll your pastry. Place a cake tin of about 18cm diameter on the pastry and cut around it, to create a disc of puff pastry. Run a sharp knife around the pastry, about 1cm from the edge, and about 1mm deep. This concentric circle will enable the pastry to rise perfectly around the apples. Line a baking tray, and place the disc onto it. Reserve in the fridge.
Peel and core the apples. Halve each apple lengthways, and cut each half into three equal-sized segments lengthways.
Melt the butter and mix it on a separate baking tray with the Demerara sugar, cinnamon, lemon juice and the Calvados (or water). Roll the apple
segments in the sugary mixture, so that they are well coated.
Roast for 10 minutes. Turn over the apple pieces, baste them, and return them to the oven for a further 10 minutes. Remove the tray from the oven,
and reduce the oven temperature to 190°C/170°C fan/gas 5. Baste the apples once more, and leave them to cool.
Arrange the apple segments on top of the pastry in a circle – leaving the space of about 1cm from the edge of the disc – to form a dome of apple
pieces. Brush them with the remaining syrup from the baking tray.
Bake in the oven (at the reduced temperature of 190°C) for 25–30 minutes.
Enjoy Tarte Boulangère warm or at room temperature. Sprinkle with flaked almonds, if using, dust with a little icing sugar and serve with a jug of
cream, a bowl of whipped cream or with ice cream or crème fraîche.