Start by preheating your oven to 350°F. Chop the onions and green bell peppers, grate the cheese, and season the chicken with salt, pepper, garlic powder, and paprika. This step sets the base for a flavorful bake.
In a bowl, combine the cream of mushroom soup and sour cream until smooth. I like to taste the sauce here to adjust salt or add extra garlic for a punchier flavor.
Place the cooked rice in the bottom of your baking dish. Lay the chicken breasts on top, then pour the creamy sauce evenly over them. Sprinkle the chopped onions, bell peppers, and shredded cheese on top for that golden finish.
Cover the dish with foil and bake for 30 minutes, then remove the foil and bake another 15 minutes. The cheese should be bubbly, and the chicken fully cooked at an internal temperature of 165°F.
Let the dish sit for 5 minutes after baking to allow the flavors to settle. I find this makes it easier to cut and serve while keeping the chicken juicy.