Roll out the pie dough on a lightly floured surface to fit a 9- or 10-inch deep-dish pie plate. Fit the dough into the pie plate and crimp the edges decoratively. Refrigerate, covered, for at least 30 minutes or up to a day.
Preheat the oven to 375°F.
Remove the pie shell from the refrigerator and line it with aluminum foil. Fill the shell with ceramic pie weights or dried beans, and bake for 13 minutes, or until lightly golden around the edges. Remove the foil and weights, return the shell to the oven, and bake for 3 minutes.
Remove the pie crust from the oven and place it on a wire rack. Lightly beat the egg white with a fork. Using a pastry brush, lightly coat the entire surface of the warm pie crust with the egg white (you will probably not use all the white). Then allow the pie shell to cool and the white to set. It will look glazed.
Slice the tomatoes into 1/4-inch-thick rounds, discarding the stem and root ends. Season the tomatoes with the salt and pepper.
Combine the mayonnaise with the egg yolk in a small bowl, and stir until smooth.
Sprinkle one third of the breadcrumbs over the bottom of the cooled pie crust. Layer half of the sliced tomatoes over the breadcrumbs in a circular pattern, and top with half of the sliced onions. Drizzle in half of the mayonnaise mixture, and top with half of the herbs, half of the Fontina, half of the mozzarella, and half of the remaining breadcrumbs. Make a second layer with the remaining tomato slices, onions, mayonnaise mixture, herbs, Fontina, mozzarella, and breadcrumbs. Drizzle the olive oil over the top, and sprinkle with the Parmesan cheese.
Bake the pie in the oven for 50 minutes to 1 hour, until it is bubbly hot and golden brown. Allow it to cool for at least 30 minutes or up to 5 hours before serving. This pie is at its best at room temperature.
Yield: 6 to 8 servings