Dredge each filet in 4 ounces of melted butter. Coat with blackening seasoning to taste. Place in a hot, heavy iron skillet. Brown each side for about 7 minutes.
In a medium sized pan, sauté the onion, bell pepper, celery and garlic in the butter until they are tender or clear, about 5 minutes. Add the flour and stir until the roux has a blonde color. Add the tomato paste, mix well. Add the salt, pepper, 1 cup of water and crawfish tails. Simmer for about 15 - 20 minutes. Adjust consistency with the remaining 1/2 cup of water if necessary.
Serve with crawfish étouffée on top blackened catfish. Garnish with green onions or parsley. Tip: Serve over rice or mashed potatoes.