Preheat the oven to 350 F. Lightly grease a 9x13-inch baking dish with non-stick cooking spray.
Cook the pasta noodles to al dente. Drain well.
Seed and chop the red bell pepper.
In a large skillet, brown the ground beef with the chopped red bell pepper, minced onion and garlic powder. Once browned, drain and then mix in the jars of marinara sauce.
In a large mixing bowl, mix together the sour cream, egg and grated Parmesan cheese.
To the prepared baking dish, layer in the cooked pasta, sour cream-cheese mixture, beef sauce and then top with the shredded mozzarella cheese.
Cover with foil and bake in the preheated oven for 30 minutes, and then uncover and bake for another 15 to 10 minutes, or until cheese begins to golden.
Prepare the salad.
Serve Baked Spaghetti with side salad.