Start the marinara sauce recipe and add the can of diced tomatoes. Let it simmer while you prepare the chicken.
Meanwhile, pound the chicken breasts to 1/2" thickness between two pieces of plastic wrap. Generously salt and pepper both sides of the flattened breasts.
Tear the bread into pieces and process in a food processor. Add 3 tablespoons of the Parmesan cheese and pulse to combine.
Set up separate bowls of flour, beaten eggs, and bread crumbs, then dredge all of the chicken breasts, first in the flour, then the eggs, then bread crumbs. Set aside.
Preheat the oven to 450°F and grease a large sheet pan.
Heat the canola oil in a large skillet on medium heat until shimmering, then add two of the breasts and saute for 2 minutes, then flip the breasts and saute another two minutes. Remove from the skillet and place on the sheet pan. Repeat with the remaining chicken breasts.
Spoon about 1/4 cup marinara sauce over the top of each breast, then generously add Parmesan and mozzarella cheese.
Bake for 12 to 15 minutes until the cheese is melted and is just starting to brown.
Serve over pasta with additional marinara sauce.