Stir together ketchup and next 6 ingredients in a small saucepan over medium-low heat; cook ketchup mixture 10 minutes, stirring occasionally.
Sprinkle catfish with pepper; arrange in an even layer in a lightly greased aluminum foil-lined broiler pan. Pour sauce over catfish.
Bake catfish at 400° for 10 to 12 minutes or until fish flakes with a fork. Garnish, if desired.