Place the banana peppers, chopped shallot, garlic, salt and ground red pepper in a blender. Pulse until the mixture is a paste

Place the beef tenderloin cubes in a skillet over medium heat with the pepper mixture, galangal, lemongrass, lime leaves and tumeric. Cook the beef with the seasonning, stir occasionally, until the meat is no longer pink inside and the meat juice have mostly evaporated. About 15 min

Pour the coconut milk into the skillet, bring to a boil, reduce the heat, and simmer for about 15 min. Remove the piece of beef to a bowl and let the coconut milk continue to simmer until thickened, about 30 min. Return the beef to the coconut sauce, reduce the heat to low, and the barely simmer the beef and the sauce until the sauce turns Brown and the oil has separated from the coconut milk, about 2,5 hiurs. Stir frequently as the sauce thickens