Pour boiling water over to cover. Let stand until tomatoes are very soft, about 30 minutes. Drain, reserving 4 tablespoons soaking liquid.
Transfer tomatoes to processor.
Add olives, onion, chopped basil, parsley and garlic and chop finely. Season with salt and pepper. Sprinkle sea bass with salt and pepper. Grill or broil fish until opaque in center, about 4 minutes per side. Transfer fish to plates.