Marinate fish in turmeric, salt, and 1 tablespoon of fish sauce. Let stand for 15 minutes. Heat oil in a large skillet, saute onion, garlic and ginger until light brown. Stir in paprika. Add tomato and remaining fish sauce. Stir fry 2 minutes. Add fish pieces one by one, fry 2 minutes without turning. Add water and shake pan vigorously to mix flavors. Do not stir or fish will break up. Cook for 2 more minutes. Sprinkle with cilantro and serve over rice.