Preheat oven to 200 C / Gas 6. Grease an ovenproof flan dish or tart tin.
Sift the flour and salt into a bowl and rub in 85g (3 oz) butter until the mixture resembles fine breadcrumbs. Stir in 85g (3 oz) of sugar and mix well. Press the crumble base mixture into the prepared dish or tin.
Over the crumble base, spread the apple purée and arrange the apple slices on top. Over the apples sprinkle the cinnamon, the remainder of the sugar and dot with the remainder of the butter.
Bake in the preheated oven for 30 minutes until the apples are golden and soft.
Remove from the oven and allow to cool before slicing and serving.