Rinse your fish and pat dry using paper towel.
Using a sharp knife make diagonal incisions on both sides of the fish, about 2 inches apart and rub the salt through the fish.
Blend all the paste ingredients together until combined and smooth.
In a deep non-stick frypan or small non-stick pot; heat the oil on high. It is important that when the paste hit the pot there is a rapid sizzling sound. (See note 1)
When the oil is hot add the paste and keep mixing to ensure the paste doesn't catch onto the pot. The paste need to keep frying on high heat until the oil and gravy move as one and the raw paste smell is gone. (See note 2)
When the raw smell is gone reduce to medium heat and add the fish curry powder. Continue frying to release the aromas.
Add the tamarind paste, fish sauce and water. Adjust to taste and allow to simmer.
Once cooked place barramundi on serving platter containing the Asam Pedas sauce. Top with more Asam Pedas sauce and coriander for garnish.
Serve with white rice and enjoy!
Note 1: The onion paste needs to literally fry, like shallow fry in the oil. A failure to ensure high heat when the paste hits the pan means that the paste will struggle to lose the raw smell and taste that comes from caramalisation.
Note 2: The paste needs to be suspended and somewhat swimming in the oil. If the ratio of oil to paste is a bit off feel free to add in more oil to the pot to encourage full caramelization.