1. Heat oven to 400°F.
2. In small skillet, sauté onion slices in 2 Tbsp. butter; set aside.
3. Spray 13" x 9" pan with nonstick cooking spray.
4. In small bowl, mix dill weed, garlic powder, salt and pepper.
5. Place fish in prepared pan; sprinkle evenly with herb mixture.
6. Layer onions, crumbs and cheese over herbs.
7. Cut butter into small pieces and sprinkle over top.
8. Bake at 400°F. for 15 to 20 minutes, or until fish flakes easily with a fork.
9. Squeeze fresh lemon over fish, if desired.