Saute ground beef and chopped onion in a medium skillet until onion is tender. Add tomato sauce, salt, oregano, basil and pepper to the skillet. Heat to boiling, reduce heat and simmer 5 minutes, stirring occasionally.
Combine cottage cheese and egg and mix well. Layer half of the zucchini in a lightly greased 8x12-inch baking dish. Sprinkle with 1 tablespoon flour. Add a layer of cottage cheese, then layer on half of the beef mixture. Add another layer of zucchini and sprinkle with 1 tablespoon flour.
Sprinkle with the mozzarella, then top with the remaining beef mixture. Bake in an oven preheated to 375 degrees for 40 minutes, until lasagna is hot and bubbly and zucchini is tender. Let stand 10 minutes before serving. Serves 6.