Soak the Dried red chilies and a piece of the Tamarind pulp (asam jawa) in warm Water for 15–20 minutes to soften, then squeeze the tamarind to extract the sour juice and reserve the soaking liquid.
Blend the rehydrated chilies with peeled Shallots, Garlic, a knob of Fresh turmeric (or turmeric paste), and a small spoonful of Belacan (shrimp paste) to form a smooth, fiery paste—add a little of the reserved tamarind liquid if needed to help the blender.
Heat a few tablespoons of Cooking oil in a wide pan or wok over medium heat, then fry the chili-turmeric paste until fragrant and the oil separates, about 5–8 minutes.
Bruise and add the Lemongrass stalks and torn pieces of Torch ginger bud (bunga kantan) to the pan, stir for another minute, then add chopped Tomatoes and cook until they start to break down and meld into the paste.
Pour in the reserved tamarind-soaking liquid and more Water to create a soupy broth, bring to a gentle boil, then reduce to a simmer so the flavors marry—taste and adjust the sourness with extra tamarind juice if desired.
Add the Okra (lady's fingers) and simmer for 3–4 minutes until just tender, then gently slide in the Spanish mackerel steaks (tenggiri), poaching them on a low simmer until cooked through, about 6–8 minutes depending on thickness.
Tear in the Daun kesum (Vietnamese coriander / laksa leaves) in the last minute of cooking for a bright herbal lift, then season the stew with Salt and a pinch of Sugar to balance the sour and spicy flavors.
Serve the Asam Pedas hot with steamed rice, spooning plenty of the tangy broth and vegetables over the fish.
