Place trout filets in rectangular-shaped aluminum cake pan. Sprinkle several drops lemon juice over each fillet. Sprinkle salt and celery salt over each filet. Slice onion into 18 thin slices. Place 3 sliced on each filet. Slice one stick butter into 18 pats. Place one pat on each onion slice. Cover pan with aluminum foil and place in preheated 325 degree oven. Bake 1-1/2 hours. If desired, you may remove pan from oven, halfway during baking period and baste filets. Return to oven and finish baking process.
