Fry the dried anchovies until crispy, drain and set aside.
Blend the shallots, chillies, garlic and belacan together until fine.
Heat a little oil in pan and fry the blended spice ingredients until fragrant. Add the onion rings and stir well for a few minutes until the onion softens a little.
Add tamarind juice, salt and sugar. Cook until the sauce thickens and then add the crispy fried anchovies.