Preheat the oven to 350°F (175°C) and grease a casserole dish lightly.

Cook the chicken breasts in a pot over medium heat for 6-7 minutes on each side. Ensure fully cooked and shred into bite-sized pieces.

Boil a large pot of salted water, add spaghetti and cook until al dente for about 8-10 minutes. Drain and set aside.

In a mixing bowl, combine shredded chicken, cooked spaghetti, cream of chicken soup, bell peppers, paprika, cayenne pepper, and garlic powder. Stir in half of the cheddar cheese.

Pour the mixture into the greased casserole dish and top with the remaining cheddar cheese. Bake for 25-30 minutes.

Let the casserole rest for 5 minutes before serving, and garnish with chopped green onions.