Prepare pie dough. Place half of dough in freezer. (You want to freeze it for about twenty minutes, beyond that and it is too cold to work with, although, if you let it warm up a bit, it will be okay).
Prepare apples. Toss with lemon juice, rhubarb, cornstarch, sugar, and cinnamon.
Preheat oven to 425°F.
Line a 9 inch quiche pan with pastry dough. Mound fruit filling into quiche shell. Remove frozen dough from freezer. Shred on a hand grater. Spread shredded dough over top of the pie.
Place quiche pan on a cookie sheet and place on lower rack of oven. Bake twenty minutes then reduce heat to 400°F and bake until top is golden brown and you can see some juices bubbling through (about 45-55 minutes).
Remove from oven and sift confectioner's sugar over top.