Preheat the oven to 375°F.
In a large skillet, cook Italian sausage, ground beef, onion, and garlic until the sausage is no longer pink and the onion is tender. Drain excess fat.
Stir in tomatoes, tomato paste, sugar, salt, basil, fennel, and pepper. Bring to a boil, then reduce heat and simmer for 20 minutes.
If using regular noodles, boil them according to package instructions, then drain. If using oven-ready noodles, skip this step.
In a medium bowl, mix ricotta cheese, egg, parsley, and salt.
In a 13x9-inch baking dish, spread 1 ½ cups of the meat sauce. Layer with one-third of the noodles, followed by one-third of the meat sauce, ricotta mixture, mozzarella cheese, and Parmesan cheese. Repeat layers two more times.
Cover the lasagna with aluminum foil and bake for 25 minutes.
Uncover and bake for an additional 20 minutes until hot and bubbly.
If the top is not browned enough, increase the oven temperature to 500°F for a few minutes, but watch carefully to avoid burning.
Let the lasagna stand for 10 minutes before cutting.