1Preheat your oven to 200°C (400°F). Line a baking sheet with parchment paper.
Peel, core, and thinly slice the apples. Place them in a bowl and toss with lemon juice, 30g of the sugar, rosewater, and ground cinnamon. Set aside.
On a lightly floured surface, roll out the puff pastry sheet to a 30cm (12-inch) circle. Transfer it to the prepared baking sheet.
Arrange the apple slices in the center of the pastry, leaving a 4cm (
5-inch) border all around.
Fold the edges of the pastry over the apples, pleating as you go, to create a rustic edge. The center will remain exposed.
Melt the butter and brush it over the apples and the pastry edges. Sprinkle the remaining 20g sugar over the apples and pastry.
Roughly chop the pistachios and sprinkle them over the apples.
Bake for 30–35 minutes, or until the pastry is golden and crisp and the apples are tender.
Allow the galette to cool slightly before serving. Enjoy warm or at room temperature.