Preheat oven to 350°.
Cook meat in a large nonstick skillet over medium heat until browned, stirring to crumble. Drain well, and return meat to pan. Stir in salt, pepper, and tomato sauce. Bring to a boil; reduce heat, and simmer for 20 minutes. Combine the sour cream, green onions, and cream cheese in a small bowl, and set aside. Place the spaghetti noodles in a 2-quart casserole dish coated with cooking spray. Spread the sour cream mixture over spaghetti noodles. Top with meat mixture. Sprinkle with cheddar cheese. Cover and bake at 350° for 25 minutes. Uncover; bake an additional 5 minutes or until cheese is bubbly.