To prepare the marinade, combine the first 3 ingredients in a large zip-top plastic bag, and seal. Marinate in refrigerator for 20 minutes. Remove fillets from bag, and discard marinade. Place the fillets, skin sides down, on a jelly-roll pan coated with cooking spray.
Preheat oven to 450°.
To prepare sauce, combine broth and next 4 ingredients (broth through cornstarch) in a small bowl. Heat oil in a wok or large nonstick skillet over medium-high heat. Add beans and the next 4 ingredients (beans through red pepper); stir-fry 10 seconds. Add broth mixture; bring to a boil, and cook for 1 minute or until thick.
Pour black bean mixture over fillets; cover pan with foil. Bake at 450° for 17 minutes or until fish flakes easily when tested with a fork. Cut the fillets into 6 portions; serve with sauce, and sprinkle with minced onion tops.