Preheat oven to 375 degrees F.

Cook the spaghetti to al dente, according to package instructions. Drain and set aside. If the noodles are going to be sitting for several minutes, you can drizzle a little olive oil over them and toss so they don’t stick together.

Place the beef or sausage in a large skillet and cook over medium heat. Break up with a wooden spoon while cooking. until browned and no longer pink. Drain off excess fat and transfer to a plate that has been lined with paper towels. Set aside.

In the same large skillet, heat the olive oil over medium-high heat. Add the onion and cook until translucent, about 5 minutes. Add the garlic and cook for 1 minute.

Add the marinara sauce, tomatoes, basil, oregano, and red pepper flakes. Turn to low and simmer for 5 minutes. Season with salt and pepper, to taste. Stir the cooked beef or sausage into the sauce.

In a small bowl, combine the ricotta cheese, egg, and Parmesan cheese.

Spray a 9x13-inch baking pan with nonstick cooking spray. Place half of the cooked spaghetti noodles on the bottom of the pan. Pour half of the meat sauce over the noodles.

Spoon the ricotta cheese mixture over the sauce and use a spatula to spread it in an even layer. Top with 3/4 cup of the shredded mozzarella cheese.

Add the remaining spaghetti and then the rest of the sauce. Top with the remaining mozzarella cheese.