This soup from timor in eastern Indonesia has a wodersweet-sour edge to it

Ingredients:

8 cups (2 liters) water

2 lbs (1 kg) top round or sweeting beef

3 tablespoons oil

5 shallots, peeled

1 teaspoon dried shrimp paste (trasi), dry roasted

2 tablespoons shaved palm sugar or dark brown sugar

1 tablespoon sweet Indonesian soy sauce (kecap manis)

2 tablespoon tamarind juice

1 teaspoons  salt

2 to 3 red finger-length chilies, deseeded and sliced into strips

2 spring onions, cut into short lengths

Cooking Direction:

1. Bring the water to a boil in a large pot. Add the beef, reduce the heat to low and simmer until the meat is half cooked, about 15 minutes. Turn off the heat. Remove the beef from the stock and drain. Strain and reserve the stock
2. When cool enough to handle, cut the beef into cubes. Heat 2 tablespoons, of the oil over medium heat in a skillet and pan-fry the beef until cooked, 2 to 3 minutes. Remove from the heat and set aside
3. Grind the shallots, garlic, dried shrimp paste and sugar to a smooth paste in a mortar or blender, adding a little water if necessary to keep the mixture turning. Set aside
4. Heat the remaining oil in a wok over medium heat and stir-fry the ground paste until fragrant, 3 to 5 minutes, add the beef cubes and sweet Indonesian paste, until the beef Is tender, 10 to 15 minutes. Adjust the taste with more salt or tamarind juice as desired, stri in the sliced chilies and spring onions, and remove from the heat. Serve hot.

source: Authentic Food Recipes from Indonesia, Heinz Von Helzen and Lother Arsana