Blend together the salt, coriander, turmeric, ginger, garlic, shallots, and chili flakes to get a smooth spice paste.
In the same oil, add lemongrass, lime leaves, and galangal and fry until fragrant. Transfer the fried ingredients to the bowl with the browned beef.
Turn down the heat to medium low, and then add the spice paste, stirring constantly until very fragrant, about 10-15 minutes.
Now add the coconut milk to the pot along with the brown sugar.
Then add the beef and herbs and stir to combine.
Turn the heat down to medium low and loosely cover with a lid, allowing some space for steam to escape. Stir the rendang periodically and simmer for 3-4 hours until the meat is very tender.
Once the meat is tender and most of the liquid has vaporized (about 4 hours), remove the lid and turn up the heat. Stir well.