To marinade the catfish clean and make three cut into the meaty side of the catfish and place into marinade for 24 hours or more. Remove the catfish and cover with cornstarch inside and out side. Dip the catfish in cornstarch and pat off to remove extra cornstarch. Place into a deep fryer onto golden brown. Drain onto paper towel. Serve with Chinese black bean sauce. Top with diced tomatoes and green onion.