Soak the dried chilies in 1/3 cup of warm water for 15 minutes.
Heat up 2 tbsp of coconut oil in a sauté pan over medium heat. Fry the onions for 15 minutes until browned. Let cool.
In a food processor or immersion blender, purée the onions, coriander seeds, ginger, coconut, and the dried chilies with it’s soaking liquid. Set aside.
Rinse the mackerel under cold water.
Cut off the head and fins. Scoop out the guts.
Cut the fish into 3-4 steaks. Give them another rinse under cold water.
Heat up 1 tbsp of coconut oil in a large saucepan over medium heat. Add the paste and fry for 3 minutes.
Add the turmeric in and fry for another 2 minutes.
Add in the tamarind paste and water. Season with salt. Bring to a simmer.
Place the mackerel steaks and Sichuan peppercorns in the curry. Cover. Lower the heat to medium low and simmer for 10 minutes.
Garnish with cilantro.