Preheat your oven to 375°F.

For the meat sauce, heat a large Dutch oven over medium-high heat. Add the sausage and ground beef. Cook for 6 to 8 minutes, breaking up the meat as it browns.

Add the diced onion and minced garlic. Cook for about 5 minutes, stirring often, until softened. Stir in the tomato paste and cook for 1 minute, stirring constantly.

Add the crushed tomatoes, tomato sauce, sugar, Italian seasoning, salt, basil, and black pepper. Stir well and bring to a gentle simmer. Lower the heat to medium-low and let the sauce simmer for 15 to 20 minutes, stirring occasionally, until slightly thickened.

For the cheese filling, stir together the ricotta, beaten egg, parsley, salt, and pepper in a medium bowl. Set aside.

While the sauce simmers, bring a large pot of salted water to a boil. Cook the lasagna noodles according to package directions until al dente. Drain, rinse with cold water, and drain again.

Lightly grease a 9×13-inch casserole dish. Spread 2 cups of meat sauce over the bottom. Lay 4 noodles in an even layer, slightly overlapping if needed. Spread half of the cheese filling over the noodles.

Repeat the layers one more time with sauce, noodles, and the remaining cheese filling.

Spread 2 cups of meat sauce over the cheese layer. Top with the last 4 noodles and spread the remaining meat sauce over them. Sprinkle mozzarella and parmesan evenly over the top. Cover with aluminum foil.

Bake for 30 minutes. Remove the foil and bake for about 15 minutes more, until the cheese is melted and the lasagna is heated through. Turn the oven to broil and broil for 2 to 3 minutes, until the cheese is lightly browned.

Let the lasagna rest for 15 minutes before slicing and serving.