In a large saucepan, cook sausage and onion until meat is brown and onion is tender. Drain off fat. Stir in tomatoes, tomato sauce and Italian seasoning. Bring to boiling; reduce heat. Simmer, uncovered, for 15 to 20 minutes or until sauce reaches desired consistency.Advertisement
For filling: In a medium bowl, combine egg, ricotta cheese and 1/4 cup Parmesan cheese. Stir in spinach.
To assemble: In an ungreased 12x7-1/2x2-inch baking pan, arrange three of the cooked noodles. Spread with half of the filling. Top with half of the meat sauce and half of the mozzarella cheese. Repeat layering noodles, filling, meat sauce, and mozzarella cheese. Sprinkle with 2 tablespoons Parmesan cheese.
Bake, uncovered, in a 375° oven about 30 minutes or until heated through. Let stand for 20 minutes before serving.