Set the oven rack in the middle and heat the oven to 400 degrees F. While the sauce cooks or as directed on the package, soak the lasagna noodles in hot tap water.
In a large saucepan, heat the olive oil. Add the chopped onion, and cook, stirring occasionally, until transparent (about 5 minutes). After that, add the garlic and stir for another 30 seconds. Crushed tomatoes, tomato paste, marinara sauce, oregano, basil, sea salt, and freshly ground black pepper should all be added. 20 minutes of uncovered simmering at a low temperature.
Olive oil has been warmed in a big kettle. Add the chopped onion and heat while stirring until transparent (about 5 minutes). Before adding the garlic, stir for a further 30 seconds. Basil, oregano, tomato paste, crushed tomatoes, marinara sauce, sea salt, and freshly ground black pepper are suggested additions. 20 minutes of low-temperature, open-air simmering.
Make the cheese filling while the sauce and sausage are cooking. Ricotta, a cup of Parmesan, an egg, chopped parsley, sea salt, and freshly ground black pepper should all be combined in a big dish. Place aside.
Pour one-third of the beef sauce into a casserole or baking dish that measures 9" x 12" x 2". The sauce should cover the whole bottom of the dish. Then, add around half of the pasta (cover the sauce with the noodles in a single layer), half of the mozzarella slices, half of the cheese combination, and one-third of the sauce. Noodles, mozzarella, ricotta, and the leftover sauce should be added in one more layer.
Bake uncovered for 35 minutes or until the sauce is bubbling, then top with the remaining 1/4 cup of Parmesan.