Preheat oven to 350°F. Spray a 10-inch baking dish with cooking spray.
Cook spaghetti according to package directions. Drain well.
In a large bowl, combine cooked pasta, beaten eggs, melted butter, 2 tablespoons parmesan cheese, and 1/4 teaspoon salt. Toss to coat well.
Press pasta mixture onto bottom and up sides of prepared baking dish to form a crust.
In a medium bowl, mix squeezed spinach, cottage cheese, remaining 2 tablespoons parmesan cheese, and remaining 1/4 teaspoon salt.
Spread spinach mixture in center of pasta crust.
Pour pasta sauce over spinach mixture, being careful not to cover the pasta edges.
Bake for 30 minutes.
Sprinkle mozzarella cheese over sauce and continue baking until cheese is melted, about 15 minutes more.
Let stand 10 minutes before cutting into wedges to serve.