Place the swordfish in a non-metallic shallow bowl, baking dish, or a ziplock bag. Combine next 6 ingredients. Mix the marinade well and pour it over the swordfish. Marinate, refrigerated for 1 hour, turning fish several times. Remove swordfish from marinade and place in a microwave-safe baking dish. Place a slice of red onion on each steak. Cover securely with plastic wrap. Microwave on high for 5 to 6 minutes. Rotate the baking dish halfway through the cooking process. Let stand, covered, for 1 minute.