Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.

Preheat the oven to 350 degrees F (175 degrees C). Coat a 9x13-inch baking dish with cooking spray.

In a skillet over medium heat, cook ground beef until brown and crumbly. Drain excess grease.

Stir pasta sauce, bell pepper, salt, black pepper, and garlic powder into ground beef in the skillet. Bring to a boil; reduce heat and simmer for 20 minutes.

Meanwhile, combine sour cream, green onions, and cream cheese in a small bowl; set aside.

Place cooked spaghetti in the prepared baking dish. Spread with cream cheese mixture; top with meat mixture and sprinkle with Cheddar Cheese.

Cover and bake in the preheated oven for 25 minutes. Uncover and bake for 5 more minutes until cheese is bubbly.