Prepare the sardines. Clean the sardines well. Coat with a little turmeric and sea salt, leave for 10 minutes in the refrigerator, then give them a final gentle rinse and drain. Keep the fish chilled until needed.
Make the masala. Roast the dried red chillies in a little oil until fragrant, without burning them. Cool, then grind with the tamarind and teaspoon of turmeric, adding enough water to make a smooth paste.
Cook the aromatic base. Heat the coconut oil in a bisale or heavy pan. Add the pounded skin-on garlic and chopped garlic, followed by the onion, ginger and green chillies.
Add the masala. Once the onions are translucent, stir in the masala paste. Add water to reach your preferred gravy consistency. We keep it fairly thick. Season with salt and bring to a rolling boil.
Cook the sardines gently. Lower the sardines into the boiling masala one by one, then reduce to a gentle simmer. Shake or swirl the pan carefully to coat them rather than stirring with a ladle, which can break the fish. Cook until the sardines are done through and the flesh is opaque and separates easily. Cooking time depends on their size; avoid prolonged cooking that breaks them apart.
Serve, or make ahead. Serve with hot red rice. For the more settled flavour we enjoy later that day or the next day, cool and refrigerate promptly, then reheat only the portion needed before serving.