For the dough, combine dry ingredients in food processor and pulse to mix. Add butter and pulse in. Add egg and continue to pulse until dough forms a ball. Roll the dough into a 14-inch disk and line a 10-inch tart pan. Chill the dough several hours, or overnight.

Peel, core, halve and slice the apples 1/8-inch thick; arrange on pastry, overlapping. Sprinkle with cinnamon sugar. For custard, combine all ingredients; whisk by hand until smooth and well blended; strain and reserve.

Bake at 350 degrees for about 35 minutes or until apples and crust are baked through. Remove tart from oven; pour on custard cream, being careful not to let it overflow. Return tart to oven for 5 to 10 minutes or until custard is set, but not colored or puffed.