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, covering completely. Use a spatula or spoon to ensure the sauce reaches all edges.
05 - Sprinkle shredded cheddar cheese evenly over the sauced chicken. If desired, add crushed gluten-free crackers or potato chips for extra texture.
06 - Bake uncovered for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F when checked with a meat thermometer. The sauce should be bubbly and the cheese melted.
07 - Remove from oven and let the chicken rest for 5 minutes before serving. This allows the juices to redistribute. Garnish with additional chopped green onions just before serving.