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

Cook the chicken in a skillet over medium heat, 6–7 minutes per side until golden and cooked through. Shred into bite-sized pieces.

Boil salted water and cook spaghetti until al dente, about 8–10 minutes. Drain and set aside.

In a large bowl, mix shredded chicken, spaghetti, cream of chicken soup, bell peppers, paprika, cayenne, garlic powder, and half the cheddar cheese until evenly coated.

Transfer mixture into the prepared dish and top with the remaining cheese.

Bake uncovered for 25–30 minutes, until bubbly and golden brown.

Let rest 5 minutes before sprinkling with green onions and serving.