01 - Set oven temperature to 375°F.
02 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook until softened, about 3 to 4 minutes. Stir in garlic and cook for 1 minute. Add ground beef, salt, pepper, oregano, basil, and crushed red pepper flakes; cook until meat is browned, breaking it apart. Drain excess fat if necessary. Stir in tomato paste and cook 1 minute. Add crushed tomatoes, tomato sauce, and sugar. Simmer uncovered for 20 to 25 minutes, stirring occasionally, until sauce thickens. Remove from heat.
03 - In a medium bowl, combine ricotta cheese, egg, grated Parmesan, parsley, salt, and pepper. Mix until smooth and well blended.
04 - If using regular noodles, cook according to package instructions until al dente. Drain and set aside. Skip this step if using no-boil noodles.
05 - Spread 1 cup of meat sauce evenly over the bottom of a 9x13-inch baking dish. Arrange 4 noodles over the sauce. Spread one-third of the ricotta mixture over the noodles, then sprinkle 1 cup mozzarella cheese. Top with approximately 1 1/2 cups of meat sauce. Repeat layering twice more, ending with noodles and the remaining meat sauce. Sprinkle the top with remaining mozzarella and Parmesan cheeses.
06 - Cover the dish with foil, spraying the underside with oil to prevent sticking. Bake for 25 minutes.
07 - Remove foil and bake for an additional 20 to 25 minutes until cheese is golden and bubbly.
08 - Allow the dish to rest for 15 minutes before slicing and serving.