Preheat oven to 450F. Depending on the length of your fillets either grease a 8x8 or a 9x13 baking dish with olive oil. Add fish fillets and season evenly with salt.
Add butter to a medium microwave-safe bowl and carefully melt in the microwave. Stir in panko, parsley, garlic, and lemon zest. Stir to coat evenly in butter.
Spoon topping overtop of the fillets, pat down lightly to adhere slightly.
Roast for 5-7 minutes, until fully cooked. Turn on broiler, and broil for 1-2 minutes until breadcrumbs are toasted and golden brown.