Preheat oven to 400°F. Place fish on foil-lined shallow baking pan. Sprinkle with salt. Mix butter and all of the spices in medium bowl. Brush fish with 1 tablespoon of the seasoned butter.
Stir spinach, panko, bell pepper and Parmesan cheese into remaining seasoned butter. Divide mixture evenly among fish fillets, pressing lightly so mixture adheres to top of fish.
Bake 15 minutes or until fish flakes easily with a fork.