Filling: Macerate the sliced apples with the sugar, rum, orange flower water, and lemon peel overnight. Strain the apples, reserving the juice.
Sift the flour and baking powder into a large bowl, put butter and eggs into a well in the centre. Working with the fingertips gradually add 7 fluid ounces of the liquid from the apples. Work into a smooth and elastic paste with your hand and leave to rest for 2 hours.
Roll out the rested paste as thinly as possible, then transfer to a floured cloth on a large table. Working from the centre, with the palms of your hands, carefully stretch the paste to the thinness of a cigarette paper. Rest it and yourself for 1 hour.
Preheat the oven to 390 degrees F.
Brush lightly with melted butter and dust with sugar, cover with well-drained apples and roll up. Mix the remaining juice into the beaten egg and brush over the top. Bake in the oven for 50 to 55 minutes.