Cook ground beef and onion on medium high until brown. Drain fat. Add next seven ingredients; heat to boiling. Reduce heat. Simmer, uncovered, until thickened. squeeze liquid from spinach. Combine with cottage cheese. Season to taste with salt and pepper. Spoon meat mixture into 13x9" baking dish. Sprinkle 1/2 of mozzarella cheese. Top with spinach. Sprinkle remaining mozzarella on top. Bake at 350~ for 25-30 minutes until hot and bubbly.