Preheat oven to 350°F.
Mix chopped onion, 1 cup shredded cheddar cheese, salt, and pepper in a large bowl.
Add sour cream and cream of chicken soup, mix well.
Then, add hash browns and melted butter, mix until combined.
Grease 9x11 inch baking pan with non-stick cooking spray
Spoon the hash brown mixture to the pan, spread evenly.
Then, sprinkle with 1 cup shredded cheddar cheese. Bake in the preheated oven for 45-60 mins until ready.