Cook noodles according to package directions. Meanwhile, in a large bowl, combine the sour cream, mayonnaise, lemon juice, milk and salt. Stir in the spinach, stuffing mix, bread crumbs and tuna until well combined.
Drain noodles and place in a greased 13-in. x 9-in. baking dish. Top with tuna mixture; sprinkle with cheese. Cover and bake at 350° for 45 minutes. Uncover; bake 5-10 minutes longer or until lightly browned and heated through.