Season the fish with ½ teaspoon sea salt; set aside.
In a large pot over medium-high, heat oil until loose and rippling, about 1 minute.
Add the onion and cook, stirring occasionally, until completely soft, about 8 minutes. When the onion is soft, stir in tomatoes and cover. Stir and smash down tomatoes every once in a while until they cook down completely, about 7 minutes.
When the tomatoes have disintegrated, stir in cilantro, garlic, xawaash, the remaining ¾ teaspoon salt, then the coconut milk. Cover and cook for 5 minutes.
Add the fish, making sure it's immersed in the coconut milk. Cover and cook until the fish is tender, white and flaky, about 8 minutes. Take the curry off the burner as soon as the fish is done, so it doesn't overcook.
Serve over rice, soor or accompanied by a flatbread of choice.