In a large saucepan, bring the chicken stock to a boil. Turn to simmer and set this aside. In another pot, cook rice noodles according to package directions. When cooked, drain noodles and divide between 4 bowls. To the simmering chicken stock, add the ginger, garlic and cod. Cook for about 3 minutes, stirring constantly. Add the turmeric, coconut milk and simmer on medium-high heat for about 5 minutes.
Add cilantro, green onions, lemon juice, and tomatoes. Cook for about 3 minutes more. Turn off heat and season with salt and pepper to taste. Ladle over noodles and top with chopped bean sprouts. Makes 4 servings.