Marinate the Chicken: Coat the chicken pieces thoroughly with the tamarind water, mashed garlic, ½ tablespoon of salt, and ground white pepper. Let it rest for 30 minutes to absorb the flavors and tenderize the meat.
Fry until Crispy: Heat enough oil in a deep pan or wok over medium heat. Fry the marinated chicken pieces until cooked through to the bone and the outer skin turns golden, crisp, and blistered (berkulit). Remove from the oil, drain well, and set aside.
Sauté the Aromatics: Heat 2 tablespoons of fresh cooking oil in a pan or wok. Sauté the minced garlic, chopped yellow onion, and bruised lemongrass until fragrant and translucent.
Build the Tomato Base: Add the coarsely chopped red tomatoes to the pan. Stir-fry over medium heat until the tomatoes soften, wilt completely, and release their natural juices into the aromatics.
Simmer the Glaze: Pour in the tomato ketchup, ¾ teaspoon of salt, granulated sugar, and 200 ml of water. Stir well and simmer over medium heat until the liquid reduces and thickens into a rich, glossy glaze.
Coat and Serve: Return the fried chicken pieces into the pan with the tomato glaze. Toss continuously until every piece is evenly coated and the savory-sweet glaze clings to the crispy skin. Remove from heat and serve hot with warm jasmine rice.