Preheat the oven to 375 degrees F (190 degrees C).
Combine flour and salt in a bowl. Rub butter into flour and salt with your fingers. Add water to make a dough and stir with a knife. Form into a ball with your hands. Roll out the pastry evenly and line a pie dish or tart pan. Leave in the refrigerator.
Whisk the egg and sugar together in a bowl. Add the double cream slowly. Add the cinnamon. Whisk together thoroughly so the cinnamon does not make any lumps. Pour the cream mixture over the apples. Place the apple tart in the oven and bake for 25 minutes, until golden on top.
Serve with good vanilla ice cream.