Heat oven to 475'. Place frozen salmon steaks in buttered baking dish, 12x8x2 inches. Sprinkle with salt and pepper; brush with melted butter. Bake uncovered 15 minutes.

While steaks are baking, heat wine, onion and lemon juice to boiling in 1 1/2-quart saucepan; reduce heat. Simmer uncovered 5 minutes. Stir water into cornstarch; stir into wine sauce. Heat to boiling. Boil and stir 1 minute. Stir in grapes. Spoon sauce over salmon. Bake uncovered 5 minutes.