MICROWAVE water and tamarind in medium microwaveable bowl on HIGH 1 min. Mash with fork; let stand 5 min. Strain tamarind through fine-mesh sieve over bowl; firmly press strained tamarind to remove all liquid. Reserve strained liquid in bowl; discard tamarind in sieve. Add coconut milk, dressing, red chili powder and turmeric to reserved liquid; mix well.
HEAT oil in large skillet on medium heat. Add next 7 ingredients; cook and stir 5 min. or until onions are crisp-tender. Stir in tomatoes; cook and stir 5 min. Add coconut milk mixture; stir. Bring to boil. Add fish; cover. Simmer on medium-low heat 10 min. or until fish flakes easily with fork.
TRANSFER fish to platter; top with sauce.
serving size = 2/3 cup (150 mL)