Preheat oven to 350. Grease a Quiche pan.
Using a pastry knife cut butter into cassava flour and salt.
Once it resembles small pea size bites add beaten egg and water.
Combine until the dough starts to form.
The dough will be more sticky than wheat flour dough.
Place two sheets of plastic wrap on your counter, place dough on top of plastic wrap.
Place two more sheets of plastic wrap on top of the dough.
Take your rolling pin and roll out the dough.
Once, you get the size you need to take off the top two pieces of plastic wrap place the quiche pan upside down on the dough, and carefully fill the quiche pan over with the dough inside.
Line the quiche pan with dough trimming the excess by pushing down on the top edge of the quiche pan.
Prick holes in the bottom of the dough.