In a large saucepan, saute onion, celery and garlic powder in oil until tender. Stir in the tomatoes, tomato paste, parsley, oregano, 1/2 teaspoon salt, 1/4 teaspoon pepper and bay leaf. Bring to a boil. Reduce heat; cover and simmer for 1 hour. Discard bay leaf.
In a large skillet, cook beef over medium heat until no longer pink; drain and set aside. In a shallow dish, combine flour and remaining salt and pepper. Place buttermilk in another shallow dish. Dip eggplant in buttermilk, then in flour mixture.
In a large skillet, cook eggplant in batches in 1/2 in. of hot oil until golden brown on each side; drain.
Place half of eggplant in a greased 13-in. x 9-in. baking dish. Top with half of Parmesan cheese, beef and tomato mixture. Sprinkle with 1 cup mozzarella cheese. Top with remaining eggplant, Parmesan cheese, beef and tomato mixture.
Bake, uncovered, at 350° for 30 minutes or until heated through. Sprinkle with the remaining mozzarella cheese. Bake 5-10 minutes longer or until cheese is melted. Let stand for 10 minutes before serving. Sprinkle with parsley. Yield: 8 servings.