Preheat the oven to 375°F (190°C). Place a rack in the middle of the oven so the chicken cooks evenly and the topping browns without burning.
Prepare the baking dish: Lightly grease a 9x13-inch baking dish with nonstick spray or a thin layer of oil. This prevents sticking and makes cleanup easier.
Prep the chicken for maximum juiciness: Trim any excess fat. Pat each chicken breast dry with paper towels so the topping adheres well. If pieces are very thick (over about 1 inch), place them between two sheets of parchment and gently pound to an even thickness. Even thickness is the easiest way to avoid dry edges and undercooked centers.
Mix the creamy topping: In a medium bowl, combine sour cream, garlic powder, seasoned salt, black pepper, and 1 cup of the grated Parmesan. Stir until completely smooth and thick. If your sour cream is very cold and stiff, let it sit at room temperature for 5 minutes so it mixes more easily.
Arrange chicken correctly: Place chicken breasts in the prepared dish in a single layer. Leave a little space between pieces so heat can circulate. Overlapping can cause uneven cooking and extra liquid in the pan.
Coat generously: Spoon the sour cream mixture over the top of each chicken breast and spread into an even layer. Aim for full coverage, especially on the thicker parts. The creamy layer helps lock in moisture while baking.
Add the Parmesan finish: Sprinkle the remaining 1/2 cup Parmesan evenly over the coated chicken. This creates the golden top and gives an easy baked chicken parmesan style flavor.
Bake until just done: Bake uncovered for 25 to 30 minutes, depending on thickness. Start checking at 22 minutes if your chicken is thinner. Use an instant-read thermometer inserted into the thickest part. The chicken is done at 165°F (74°C). Pulling it right at temperature is key for a juicy baked chicken breast.
Optional golden top: For a more golden cheesy finish, switch the oven to broil for 2 to 3 minutes at the end. Keep the dish on the middle rack and watch closely, as Parmesan can brown quickly.
Rest before slicing: Remove from the oven and let the chicken rest for 5 minutes. Resting allows juices to redistribute so they stay in the meat when you slice, keeping the texture moist and tender.
Serve: Serve warm with rice, roasted vegetables, salad, or pasta. Spoon any creamy pan sauce over the top for extra flavor.