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

In a large pot over medium heat, cook chicken breasts for 6-7 minutes on each side until golden brown and cooked through.

In salted water, cook spaghetti until al dente (about 8-10 minutes). Drain and set aside.

In a large bowl, combine the shredded chicken, cooked spaghetti, cream of chicken soup, chopped bell peppers, paprika, cayenne pepper, garlic powder, and half of the cheddar cheese. Stir until everything is evenly coated.

Transfer your mixed ingredients to the greased casserole dish, and sprinkle the remaining cheddar cheese on top.

In the preheated oven, bake for 25-30 minutes until bubbly and golden brown.

Let the casserole rest for 5 minutes before garnishing with sliced green onions and serving.