Combine sake and next 3 ingredients in large skillet, bring liquid to boil, reduce heat and simmer for 5 minutes. Arrange fish on rack and sprinkle with salt and pepper. Place rack in skillet. Top fish with onions, drizzle with soy sauce and sesame oil. Cover skillet; steam fish until opaque in center, about 5-7 minutes. Remove steamer rack and mix cilantro into juices in skillet. Spoon rice on plates and top with fish, juices from skillet, and toasted sesame seeds.