In a large mixing bowl, whisk together flour, salt, and sugar until well combined. Cut in cold butter until mixture resembles coarse crumbs. Gradually add ice water, mixing until dough holds together. Refrigerate for at least 30 minutes.

Combine raspberries, granulated sugar, cornstarch, salt, lemon juice, and vanilla extract in a bowl. Let sit for 10 minutes.

Preheat oven to 400°F (200°C). Roll out one dough disc to fit a 9-inch pie dish. Pour in raspberry filling and dot with butter. Roll out second dough disc, place over filling, and crimp edges.

Cut slits into top crust for ventilation. Brush with whisked egg and sprinkle with coarse sugar.

Bake pie for 50 minutes or until golden brown and filling is bubbling. Cool on wire rack for at least 2 hours before serving.