Preheat oven to 350°F (177ºC).

Make Sauce: Heat olive oil (2 tablespoons), over medium-high heat, in a large, high-sided skillet. Add onion (1 cup) and saute until translucent, about 5-7 minutes. Moderate heat so as not to brown onion. Turn heat to medium-low, add minced garlic (1 tablespoon), and cook until fragrant, 1-2 minutes.

Add beef (2 pounds), salt (1 ½ teaspoons), and black pepper (1 teaspoon) to skillet and cook, over medium heat, until no longer pink; drain as needed. Stir in spaghetti sauce (2 jars) and add Italian seasoning (3 teaspoons).

Make Ricotta Filling: In a large bowl, combine ricotta cheese (24 ounces), eggs (2), nutmeg (¼ teaspoon), Italian seasoning (1 teaspoon), mozzarella cheese (1 cup), and Parmesan (1 cup).

Pasta: Cook pasta (12 ounces) according to package directions. Drain well.

Assembly: Add ½ cup of sauce to the bottom of a 13x9-inch baking dish and swirl to cover the bottom. Spread ½ of cooked pasta in the baking dish, then spoon a ½ of the meat sauce, then dollop ½ ricotta mixture-spreading it into an even layer with an offset spatula. Repeat with remaining layers, ending with ricotta mixture.

Place filled baking pan on a rimmed cookie sheet.

Cover and bake for about 40 minutes or until a thermometer reads 160°. Uncover; sprinkle with remaining 2 cups mozzarella cheese. Bake 10 minutes longer or until cheese is melted. Let stand 15 minutes before serving.