1. Preheat your broiler. Line a baking pan with foil and spray foil with non-stick spray.
2. Combine miso, vinegar, hot water, lemon juice, soy sauce, sugar, ginger and garlic in a small bowl and beat with a whisk until smooth.
3. Place cod in the baking pan and sprinkle with pepper.
4. Spread miso mixture on the top of each cod fillet.
5. Broil the fish 5 inches from the heat until just opaque in the center, 5-8 minutes.