Preheat your oven to 425°F.
In a medium saucepan, combine the crushed pineapple (with its juice), granulated sugar, cornstarch, and lemon juice. Stir continuously over medium heat until the mixture thickens and begins to bubble. Remove from heat and allow to cool slightly.
Roll out half of your double pie crust and line a 9-inch pie dish. Pour the cooled pineapple filling into the crust.
Roll out the remaining pie crust and place over the filling. Trim excess crust from the edges and pinch to seal. Cut slits in the top crust to allow steam to escape during baking.
Brush the top crust with the beaten egg and water mixture to give your pie a beautiful golden finish.
Bake in the preheated oven for 35-45 minutes, or until the crust is golden brown.
Allow the pie to cool on a wire rack before serving. Enjoy your pineapple pie warm or at room temperature.