Cook spinach until thawed, then drain and squeeze dry. Add onions and set aside.
Combine Monterey Jack cheese, cottage cheese and eggs. Divide cheese mixture into 2 equal parts and place in 2 bowls. Add spinach mixture to one bowl, blending well. Arrange a layer of noodles in a well-buttered shallow baking dish. Cover with the cheese-spinach mixture and dot with butter. Place another layer of noodles on top and cover with the plain cheese mixture. Sprinkle with Cheddar cheese and sprinkle with a little paprika. Bake for 30 minutes or until bubbly and cooked through.