In large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Add tomato sauce and seasonings. Bring to boil; simmer, uncovered, for 5 minutes.
Meanwhile, cut zucchini into 1/4-in. slices. In small bowl, combine cottage cheese and egg. In a greased 3-qt. baking dish, place half of the zucchini; sprinkle with half of flour. Top with cottage cheese mixture and half the meat mixture. Repeat layer of zucchini and flour.
Sprinkle with mozzarella cheese and remaining meat mixture. Bake at 375° for 40 minutes or until heated through. Sprinkle with additional cheese if desired. Let stand for 10 minutes before serving. Yield: 6-8 servings.