Preheat your oven to 350 degrees. Spray a 9 by 13 inch baking dish with cooking spray.
Bring a large pot of water to a roaring boil. Add the lasagna noodles and cook according to the time indicated on the box. When the noodles are done cooking and have been drained, spread them on lightly greased baking sheets while you finish the sauce and make the filling.
12 ounces lasagna noodles
While the noodles are cooking, heat a large skillet over medium heat. Add the olive oil. Add the onion and garlic, cooking until the onion begins to soften, about 3 minutes.
1 tablespoon olive oil, 1 small yellow onion, 3 cloves garlic
Add the Italian sausage, breaking it up. Cook until it is well broken up and just begins to brown, about 3 minutes. Drain off any excess grease.
1 pound Italian sausage
Add the tomato sauce, salt, oregano, basil, sugar, red pepper flakes and pepper to the meat mixture and set aside. Simmer on low for 5 minutes. Taste and add more salt, pepper, and/or sugar to taste.
28 ounces tomato sauce, 1 tablespoon dried oregano, 1 tablespoon dried basil, 1 1/2 teaspoons sugar, 1 1/2 teaspoons kosher salt, 1/4 teaspoon red pepper flakes, 1/4 teaspoon black pepper
Set aside 1 1/2 cups of mozzarella and 1/4 cup of parmesan cheese.
In a large bowl, mix together the ricotta, eggs, and the remainder of the mozzarella and Parmesan. Divide the mixture into thirds.
Add a ladle full of the sauce and meat mixture to the baking dish, spreading it to coat the bottom. Add a layer of lasagna noodles. Top the noodles with 1/3 of the cheese mixture and then more sauce and meat. Repeat until you have used all the ingredients (save the set aside cheese). Finally, top with the set aside cheese.
Bake uncovered for 30 minutes. Broil for 5 minutes at the end if you would like the cheese to be more browned. Let stand for 10 minutes before slicing and serving.