Melt the 75 g butter and 100 g sugar in a saucepan over medium heat until it turns into a golden caramel.
Add the 1 tsp cinnamon, and pour the caramel into the bottom of a solid tart tin or cake tin (Ø 16 cm) without a removable base.
Arrange the 4 pcs apples, peeled and cut into wedges, in a tight pattern on top of the caramel. Bake the apples without the pastry in the airfryer at 180 °C for 10 minutes, so they soften slightly and the juices cook down into the caramel.
Carefully take the tin out (it is very hot), and cover the apples with the 1 sheet puff pastry, rolled out and trimmed to fit the tin. Tuck the edges down along the side of the tin, and prick a few holes in the pastry.
Continue baking at 180 °C for 20-25 minutes, until the puff pastry is golden and crisp and the caramel is bubbling thickly around the edge.Start the online kitchen timer here
Leave the tart to rest for 5 minutes. Place a plate over the tin and flip it quickly using oven gloves – the caramel is still very hot.
Notes
Use a solid tart tin or cake tin (Ø 16 cm) without a removable base – the runny caramel will leak out of a springform tin.Best served warm with a scoop of vanilla ice cream or crème fraîche.