Preparation

• In a large bowl, mix together the rhubarb, sugar, cornstarch, lemon juice, and salt.
• Roll out each batch of pie dough on a floured surface into two circles, each 12 inches in diameter.
• Place one circle into a 9-inch glass pie plate and fill it with the rhubarb mixture.
• Dot the filling evenly with cold butter, then cover it with the second dough round and trim the excess dough to about 1 inch.
• Fold the edges of the top dough underneath and crimp the edges to seal.
• Make five 1-inch slits in a circle on the top crust to allow steam to escape, then freeze the pie for 30 minutes.
• Preheat the oven to 375°F, positioning a rack in the middle and another in the bottom third.
• Brush the top crust with the egg wash and sprinkle it generously with sanding sugar.
• Bake the pie on the middle rack, placing a baking sheet lined with foil on the bottom rack to catch any juices. Bake for about 1 hour.
• Monitor the browning of the top crust; if it darkens too quickly, cover it loosely with foil. Continue baking, checking every 10 minutes, for about another 30 minutes, until the pie is bubbling in the center and the bottom crust is golden.
• Once done, move the pie to a cooking rack to cool completely.