Boil the Pasta: Cook the spaghetti in a large pot of salted water until al dente (check the package for timing). Drain and set aside.
16 ounces spaghetti
Brown the Meat: Heat olive oil in a skillet over medium heat. Add the ground beef and cook until no longer pink, breaking it into crumbles. Drain any excess fat.
1 tablespoon olive oil, 1 pound ground beef
Sauté the Aromatics: Toss the onion and garlic into the skillet with the meat. Cook for 2–3 minutes until softened.
1 small onion, 3 cloves garlic
Simmer the Sauce: Stir in the marinara sauce, diced tomatoes, oregano, basil, red pepper flakes, salt, and pepper. Let it simmer for 10 minutes to thicken slightly.
24 ounces marinara sauce, 14.5 ounces canned diced tomatoes, 1 teaspoon dried oregano, 1 teaspoon dried basil, Salt and black pepper to taste, ½ teaspoon red pepper flakes
Combine Pasta and Sauce: Dump the drained spaghetti into the skillet and toss until fully coated with the meat sauce.
Layer the Dish: Spread half the spaghetti mixture into the greased baking dish. Dollop spoonfuls of ricotta (if using) over the top, then sprinkle with half the mozzarella and half the Parmesan. Repeat with the remaining spaghetti and cheeses.
15 ounces ricotta cheese, 8 ounces shredded mozzarella cheese, 4 ounces grated Parmesan cheese
Bake to Perfection: Pop it in the oven at 375°F for 25–30 minutes, or until the cheese is melted and bubbly with golden spots.
Garnish and Serve: Sprinkle with fresh parsley, let it cool for 5 minutes (if you can resist), then dig in.
2 tablespoons chopped fresh parsley