01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with cooking spray or a small amount of oil.
02 - Pat chicken breasts dry with paper towels. Season both sides generously with kosher salt and freshly ground black pepper. Arrange seasoned chicken in the prepared baking dish in a single layer.
03 - In a medium bowl, combine sour cream, mayonnaise, chopped green onions, dry onion soup mix, garlic powder, onion powder, and milk. Whisk until completely smooth and well incorporated.
04 - Spread the sour cream and onion mixture evenly over each chicken breast, ensuring complete coverage. Use a spoon or spatula to distribute the sauce thickly across the surface.
05 - Sprinkle shredded cheddar cheese evenly over the sauced chicken. If desired for added texture, top with crushed gluten-free crackers or potato chips.
06 - Bake uncovered for 25 to 30 minutes, or until chicken reaches an internal temperature of 165°F when tested with a meat thermometer. The sauce should be bubbly and the cheese melted and lightly golden.
07 - Remove from oven and let the chicken rest for 5 minutes to allow juices to redistribute. Garnish with additional chopped green onions before serving.