Preheat oven to 375°. In large skillet, cook and crumble beef with onion over medium-high heat until no longer pink, 5-7 minutes. Stir in seasonings and tomato sauce. Season with salt and pepper to taste. Bring to a boil; simmer, uncovered, 5 minutes. In a bowl, mix egg and cottage cheese.

Trim ends of zucchini; cut lengthwise into 1/4-in.-thick slices*. Layer half the slices in a 13x9-in. baking dish coated with cooking spray; dust with half the flour. Top with cottage cheese mixture and half the meat sauce. Add remaining zucchini; dust with remaining flour. Spread with remaining meat sauce; sprinkle with 1 cup mozzarella cheese.

*Raw zucchini contains a lot of water, which can result in a watery lasagna. You can avoid this by generously salting your zucchini slices and letting them rest on paper towel for 10-15 minutes. The salt will release some of the moisture. Blot the slices dry with paper towel to remove the salt and moisture. If you are in a hurry you can skip this step, but it is usually worth the effort.

Bake, uncovered, until heated through, about 40 minutes. If desired, sprinkle with additional cheese. Let stand 10 minutes before serving.