Preheat oven to 200 degrees C. Line a baking tray with aluminium foil.
Toss bread crumbs with onion, dill, lemon zest, garlic and half of the olive oil. Season with salt and pepper to taste. Press stuffing into the trout then brush the trout with the remaining olive oil and season with salt and pepper. Place trout onto prepared baking tray.
Roast in the preheated oven until the skin of the fish begins to brown and the flesh flakes easily with a fork, about 20 minutes.