Preheat oven to 375°F. Bring a large pot of salted water to a boil and cook spaghetti until al dente; drain and reserve 1/2 cup pasta water.

Brown the ground beef in a large skillet over medium-high heat until crumbly.

Add onion and garlic to the skillet and sauté until softened.

Stir in crushed tomatoes, tomato sauce, Italian seasoning, salt, and pepper. Simmer for 10 minutes until thickened.

In a bowl, combine ricotta, Parmesan, and beaten egg until smooth.

Spread 1 cup of meat sauce on the bottom of a 9x13-inch baking dish.

Layer half the spaghetti, half the ricotta mixture, and half the mozzarella over the sauce.

Repeat the layers with the remaining spaghetti, ricotta, and mozzarella, then top with the remaining meat sauce.

Bake uncovered for 25 minutes until bubbly and golden. Rest for 10 minutes before serving, garnished with fresh parsley.