Place the flour and butter in a large bowl. Cut the butter into the flour using a pastry blender until you have pieces that are pea size. Add the parmesan cheese and pepper, stir to combine.
Add the cold water a Tablespoon at a time to a small portion of the flour, tossing to combine. Push the flour to the side and repeat with the rest of the flour and water.
When all the dough is moistened , form it into a flat disk, wrap it in plastic wrap and refrigerate to chill the dough for at least 1 hour. The longer you can let the dough chill in the fridge, the easier it will be to handle.
Roll the dough out on a lightly floured surface to a 13 inch circle. Fold the pie crust in half. Place the pie crust on a parchment paper lined cookie sheet. Unfold the dough and place in the refrigerator for an hour. Refrigerating the rolled out pie crust will help to lessen the shrinkage when baking.
Remove the dough from the fridge. Combine the bread crumbs, stir to mix together. Spread the bread crumbs over the crust leaving a 2 inch border from the edges of the crust with no crumbs.
Layer the tomatoes, onion and cheese over the bread crumbs. Fold the crust over the filling so part of the filling is showing. Pleat the dough edges as needed as you go along.
Combine the egg and water, whisk to incorporate. Brush the mixture over the edges of the pie crust.
Bake at 375 degrees for 30 - 40 minutes until the crust is browned and crisp. Cool 10 minutes before cutting and serving.