Preheat your oven to 400°F (200°C) and lightly grease a large, shallow baking dish.
Pat the flounder fillets dry with paper towels and arrange them in a single layer in the prepared baking dish.
Season the fish with salt and pepper on both sides.
In a medium bowl, combine the panko breadcrumbs, grated Parmesan, chopped parsley, garlic powder, and paprika. Mix well.
In a separate small bowl, combine the melted butter and lemon juice.
Brush the top of each flounder fillet with the butter-lemon mixture.
Spoon the breadcrumb mixture evenly over the fillets, pressing gently to adhere. Drizzle any remaining butter over the breadcrumb topping.
Bake in the preheated oven for 12-15 minutes, or until the fish is opaque and flakes easily with a fork and the topping is golden brown.
If desired, broil for the last 1-2 minutes to get an extra crispy topping, watching carefully to prevent burning.
Serve immediately with fresh lemon wedges for squeezing over the top.