Catch, clean, and skin rainbow trout. Score each side at ½ inch intervals. Season with garlic powder and Cajun seasoning. Squeeze lemon juice over both sides and let sit for 30 minutes. Mix Italian bread crumbs and flour in equal portions. Add salt and pepper to taste.
Thoroughly coat damp, seasoned fish with bread crumb mixture. Preheat griddle to 375 degrees. Spread olive oil or butter on heated griddle. Cook fish until golden brown. Turn fish, adding oil or butter as needed. Turn only once.