Preheat the Oven: Set the oven to 375°F (190°C).
Prepare the Noodles: Boil lasagna noodles for 4 minutes, then drain and rinse under cold water. Set aside.
Make the Meat Sauce: In a large saucepan, combine cooked sausage or ground beef with 1 1/2 jars of marinara sauce. Simmer for 5 minutes.
Prepare the Cheese Mixture: In a bowl, mix ricotta cheese, 3 1/2 cups mozzarella, Parmigiano-Reggiano, and eggs until well combined.
Assemble the Lasagna: Grease a 9x13-inch baking dish. Spread 3/4 cup marinara sauce on the bottom. Layer 3-5 noodles, overlapping slightly. Add a layer of cheese mixture, then a layer of meat sauce.
Repeat Layers: Continue layering noodles, cheese mixture, and meat sauce two more times. Top with remaining marinara sauce and sprinkle with remaining mozzarella.
Bake: Cover with foil and bake for 30 minutes. Remove foil and bake for an additional 10 minutes until the cheese is browned.
Rest and Serve: Allow lasagna to rest for 10 minutes before slicing and serving.