1. Make tamarind juice by mixing tamarind with warm water.
2. Simmer tamarind juice with onions and dried peppers. Simmer until reduced to about 60 %.
3. Filter and then simmer it over low heat. Gradually add coconut sugar and stir well until smooth. Continue simmering for about 1 hour or until the sauce is quite thick. Season with salt or fish sauce. Ready to serve.