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.