Grandmas Rhubarb Pie with Flaky Crust

Instructions:

1. Pulse the flour, sugar, and salt in a food processor. Add chilled butter and pulse only until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
2. Gradually drizzle in ice water, pulsing until the dough just begins to clump. Divide into two discs, wrap in plastic, and refrigerate for at least 2 hours.
3. Toss the sliced rhubarb with lemon juice, cinnamon, and salt. Stir in the sugar and cornstarch, ensuring every piece is coated. Let the mixture sit for 15 minutes to macerate.
4. Roll out the first disc of dough and press it into a 9-inch deep-dish pie plate.
5. Pour in the rhubarb filling, piling it slightly in the center.
6. Roll out the second disc and place it over the top. Trim the edges, pinch them to seal, and cut 4-5 slits in the center to allow steam to escape.
7. Brush the top with egg wash and sprinkle with coarse sugar.
8. Place the pie on a baking sheet and bake at 400°F (200°C) for 60 minutes or until the crust is mahogany-colored and golden brown.