Preheat the oven to 200°C/400°F/gas mark 6 and roll out the pastry to 0.5 cm thick. Use a large dinner plate (approximately 25 cm diameter) to cut out a perfect circle from the pastry. Transfer this to an un-greased baking sheet.
Quarter and core the apples (no need to peel them unless you really want to), then cut into very thin slices. Decoratively arrange the slices on the pastry circle, slightly overlapping each other in a fan shape.
Brush the pastry and apples with the melted butter, then evenly sprinkle the caster sugar over the top of the tart.
Bake in the preheated oven for 20-25 minutes, until the apples are golden on top and the pastry is cooked through.
Dust the tart with icing sugar and serve warm with dairy-free ice cream, custard or dairy-free cream.
*Variations: Make a spiced apple galette by spreading 2 tablespoons of Lotus Biscoff spread onto the pastry before adding the apples and adding half a teaspoon of cinnamon to the caster sugar.