Finely slice green onions; reserve 1/4 cup of the green tops for garnish. In a deep microwaveable casserole bowl or 8 cup measure, combine onions. rice, tomatoes and their liquid, broth, thyme, pepper and salt (dish needs to be twice the height of these combined ingredients). Cover dish tightly and microwave on high (100% power) for 16 minutes, rotating the dish a quarter turn halfway through cooking. Remove the dish from microwave; stir in peas. Arrange mussels and shrimp alternately around the edge of dish, sticking mussels upright into the rice mixture and shrimp head down and tail toward center (they do not need to be completely covered with liquid). Arrange fish pieces in an even layer in center, on top of the rice mixture. Cover and microwave on high until most of the fish has turned opaque throughout and mussels open, 5 to 8 minutes more. Mixture will look saucy. Let stand, covered, about 3 minutes for fish to finish cooking. Serve in wide shallow bowls and sprinkle with reserved green onions over each serving. Makes 4 servings. Note: Clams, Scallops and Grouper may be substituted.