Inspired by canh chua, Vietnamese sweet and sour soup, the flavor of the broth comes from the combination of sour tamarind juice and chunks of sweet ripe pineapple.
In a pot, boil four cups of water, drop in the salmon, and pour in two tablespoons fish sauce.
Boil the fish just until done, about five minutes.
Scoop out the fish, and break the flesh into chunks as you separate it from the bones.
Put the fish bones back into the pot and simmer for ten minutes.
Strain the liquid; discard the bones.
Place the tomatoes, bell peppers, celery, okra and pineapple chunks in a clean pot, and pour in the fish stock, tamarind juice and another tablespoon of fish sauce.
Bring to the boil, cover and simmer for ten minutes or just until the okra is done.
Add the salmon chunks into the pot and continue simmering just until the fish is heated through.
Taste, stir in more fish sauce if needed, garnish with cilantro and serve.