Preheat the oven to 375°F (190°C).

In a mixing bowl, combine the breadcrumbs, melted butter, parsley, lemon juice, garlic powder, onion powder, salt, and pepper.

Rinse the haddock fillets under cold water and pat them dry with a paper towel.

Place a generous amount of stuffing onto each fillet, pressing gently to ensure it sticks.

Lay the stuffed fillets in a greased baking dish.

If using cheese, sprinkle it over the stuffed haddock.

Bake in the preheated oven for about 25 minutes, or until the fish flakes easily with a fork.

Remove from the oven and let it sit for a few minutes before serving.