Halibut " Gratin"

1 (12 ounce) package frozen halibut steaks 1/2 teaspoon salt 1/4 teaspoon dried oregano leaves 1 green onion , finely chopped 1 1/2 teaspoons dry breadcrumbs[...]

3 lbs halibut, cut into pieces 1 extra large white onion, cut into rounds 2 large leeks , cut into rounds 1 pinch saffron 5 medium tomatoes , cut in rounds 2[...]