To make pastry, sift flour and salt into a large bowl.
Using a pastry blender or 2 knives, cut in butter or margarine until evenly distributed and mixture resembles breadcrumbs.
With a fork, lightly mix in sugar, egg yolk and enough ice water to make a dough.
Press into a ball and wrap in foil or plastic wrap.
Refrigerate 30 minutes.
On a floured surface, roll out dough to fit a 9-inch (23-cm) flan tin with a removable bottom.
Place dough in tin without stretching.
Pierce bottom of pastry shell all over with a fork.
Preheat oven to 400°F (205°C).
To make filling, peel, quarter and core apples.
Thinly slice each quarter several times without cutting all the way through.
Sprinkle with lemon juice.
Arrange sliced apple quarters in pastry shell.
In a medium bowl, beat eggs and sugar until pale and creamy.
Add cream and vanilla.
Pour egg mixture over apples.
Bake 20 minutes then reduce heat to 350°F (175°C) and bake 25 milnutes longer or until custard filling is firm.
Cool slightly in tin then transfer to a rack to cool completely.