Pre-heat oven to 375° F.
In a large skillet, add onion, Italian sausage, ground beef, salt and pepper; cook until well done; drain, if necessary, and set aside.
Cook lasagna noodles; see tip below for best results.
In a large saucepan, combine cooked meat and 1-½ jars sauce; simmer 5 minutes.
In a small bowl or cup, lightly beat the two eggs.
In a large bowl, combine ricotta cheese, 3 ½ cups mozzarella cheese, Parmigiano-Reggiano cheese and eggs.
Grease a 13 x 9-inch baking dish with cooking spray.
Spread ¾ cup marinara sauce over the bottom of the baking dish.
Place 3 to 4 lasagna sheets on top of the marina sauce, slightly overlapping.
Spread 1/2 of the cheese mixture over lasagna and cover with ½ of the meat sauce.
Repeat for 1 more layer.
Cover last layer with remaining lasagna sheets and remaining marinara sauce.
Sprinkle with remaining mozzarella cheese.
Cover with foil and bake for 30 minutes.
Remove foil and bake additional 10 minutes.
Let stand 10 minutes before serving.