If making the pastry by hand, rub the butter into the flour and icing sugar until it resembles fine breadcrumbs.
Stir in the beaten egg and bring together to form a dough. This can also be done in a food processor.
Chill for about 30 minutes. Roll the dough out on a floured surface and line a round 28cm/11in (3.5cm/1½in deep) flan tin. Form a lip around the edge. Chill for a further 30 minutes while making the filling.
Preheat the oven to 200C/400F/Gas 6.
To make the filling, beat the eggs, caster sugar, lemon rind and juice together in a large mixing bowl.
Stir in the warm melted butter.
Coarsely grate the Bramley apples directly into the mixture and mix well.
Remove the tart from the fridge and spread the runny lemon mixture over the base.
Level the surface with the back of a spoon and arrange the dessert apple slices around the edge, overlapping.
Sprinkle over the demerara sugar.
Put on a heavy baking tray and bake in the oven for about 40-50 minutes until the centre feels firm to the touch and the apples are tinged brown.