Preheat and Prep: Preheat the oven to 375°F and lightly grease a 9x13-inch baking dish.
Make the Meat Sauce: Heat the olive oil in a large skillet or Dutch oven over medium-high heat.
Add the ground beef, onion, and ¼ teaspoon of the salt and cook for 5 to 6 minutes, breaking the beef into small crumbles, until no pink remains and the onion is softened, stirring occasionally.
Add the garlic, oregano, and Italian seasoning, and cook for 1 minute until fragrant, stirring frequently.
Add the tomato paste and cook for 1 minute, stirring frequently.
Stir in the crushed tomatoes, ½ teaspoon of salt, ¼ teaspoon pepper, and sugar.
Bring to a simmer, then reduce the heat to low and cook uncovered for 10 minutes, stirring occasionally, until the sauce thickens and the flavors meld together.
Cook the Noodles: While the sauce simmers, bring a large pot of heavily salted water to a boil. Cook the lasagna noodles just shy of al dente, about 8 minutes. Drain but do not rinse.
Tip: You want the noodles to be mostly cooked but still with a bite and before they start to fall apart, as they will continue cooking while baking. You can lay them flat on a sheet of parchment or foil after draining and just before layering to avoid them sticking together.
Make the Ricotta Filling: In a medium bowl, stir together the ricotta, egg, ½ teaspoon salt, and ¼ teaspoon pepper, ⅓ cup of the Parmesan and 1 cup of the mozzarella until well combined. Set aside.
Assemble: Spread 1 cup of the meat sauce in a thin layer on the bottom of the prepared baking dish. Lay 3 lasagna noodles over the sauce, overlapping slightly.
Layer with about ⅓ of the ricotta mixture (about a heaping ½ cup) and 1 cup of the meat sauce.
Repeat twice more.
Finish with 3 noodles topped with the remaining sauce, 1 cup of the mozzarella, and ⅓ cup of the Parmesan.
Bake: Cover tightly with foil, spray the underside of the foil with nonstick spray to prevent it from sticking to the cheese.
Bake covered for 25 minutes, then remove the foil and bake uncovered for 10-20 minutes more, until the cheese is golden and the sauce is bubbling around the edges.
Let the lasagna rest uncovered for 15-20 minutes before cutting.
Serve: Cut into squares and serve with fresh parsley on top.