Cook noodles; drain and place in bowl. Cook spinach; drain very well in strainer, pressing out excess liquid. Add spinach, tuna, cottage cheese, cheddar cheese, soup, lemon juice and salt to noodles. Toss lightly to mix. For freezing, place 3/4 cup in foil pans. Cover with foil; freeze. To heat, place frozen casserole on rack. Bake in very hot oven at 450° for 40 minutes. If desired, remove foil, add shredded cheese, return to oven for 2 minutes.