Preheat the oven to 350°F (177°C) and prepare a 9x13-inch baking dish with nonstick spray.

In a large skillet, heat olive oil over medium heat, add chopped onion and green bell pepper, sauté for about 5 minutes.

Stir in garlic and cook for another minute until fragrant.

Add ground beef to the skillet and cook for 7-8 minutes, breaking apart, until no longer pink; drain excess grease.

Season with salt, black pepper, and Italian seasoning, then add spaghetti sauce and mix well. Set aside.

In a large pot, bring salted water to a boil. Add spaghetti and cook according to the package instructions, 8-10 minutes.

Drain spaghetti and set aside while preparing Alfredo sauce.

In a saucepan, melt butter over medium heat, add garlic and sauté for 1-2 minutes.

Sprinkle in flour and cook for another minute, then whisk in heavy cream gradually.

Continue whisking for 3-4 minutes until the sauce is smooth and thickened.

Stir in Parmesan cheese until melted, then remove from heat.

Combine drained spaghetti with Alfredo sauce in a large mixing bowl until coated.

Layer coated spaghetti in the prepared baking dish, then top with meaty red sauce.

Sprinkle mozzarella cheese over the top and bake uncovered for about 30 minutes until golden brown.

Cool for a few minutes before serving and garnish with fresh parsley if desired.