Preheat the oven to 400ºF/205ºC degrees.
Lay the tomato slices out on paper towels and sprinkle them with kosher salt. Let sit for 30 minutes to draw some of the liquid out. After resting, dab them with paper towels to remove any liquid sitting on the surface. While the tomatoes are resting, prepare the pie crust.
Roll out your pie dough and place it in a 9-inch deep dish pie plate. Crumple a piece of parchment paper and place it inside the pie crust. Fill with pie weights.
Bake the pie shell in the preheated oven for 15 minutes. Remove from the oven, remove the pie weights and the parchment paper and set the pie shell aside.
Reduce the oven temperature to 350ºF.
Sprinkle the bread crumbs in the bottom of the pie crust.
Next, add half of the tomato slices.
Top the tomatoes with half of the onion slices and basil.
Combine the mozzarella cheese, cheddar cheese, mayonnaise and black pepper in a small bowl. Stir well.
Add about 1⁄3 of the cheese mixture to the pie.
Then add a second layer of the remaining tomatoes, followed by the onions and basil. Top with the remaining cheese mixture.
Bake in the preheated oven for about 45 minutes or until the cheese is melted and the crust is golden brown.
Remove from the oven and let it rest for about 30 minutes before slicing.