Preheat oven to 325 degrees. Cut each slice of bread into 1 inch cubes. Place bread cubes on a baking sheet and bake until lightly toasted. If you enjoy the taste of garlic, the slices can be brushed with olive oil and sprinkled with garlic powder after baking.
Heat olive oil in saucepan over medium heat. Add green onions and saute until onions are soft. Add 1/2 of the tomatoes, garlic, tomato paste, and 4 tablespoons basil. Cover pan and simmer about 10 minutes over low heat. Add remaining tomatoes and basil, crab meat, juice and/or stock, pepper, saffron threads, salt and bring to a simmer.
Place four cubes of bread in each serving bowl. Ladle hot soup over bread. Sprinkle with Parmesan cheese, if desired. Serve immediately. Makes 4 servings.