Place a single layer of the sliced tomatoes in the bottom of the prepared greased baking pan (use just half of the tomatoes for the bottom); set aside.
In a large bowl, combine the bread crumbs, Parmesan cheese (if using), 2 cups of the shredded mozza cheese, crumbled bacon, butter, celery, onion, eggs, garlic salt and oregano; mix well to combine.
Spoon all of the bread crumb mixture over the tomatoes in the baking pan.
Top with the remaining sliced tomatoes.
Sprinkle with the remaining 1 cup (or more if desired) mozza cheese.
Bake uncovered, for 30 minutes, or until heated through- DELICIOUS!
Note: garlic powder may be used in place of garlic salt, just add 1/2- 1 tsp seasoning salt, or to taste (or regular white salt, I prefer seasoning salt) to the bread crumb mixture if using just garlic powder.