In food processor, chop the nuts fine, then blend in the garlic, shallots, ginger, chiles, salt and tomato to form a paste. Rub chicken with lemon juice and let stand for 30 minutes. Heat oil in skillet and stir-fry the paste for 3 minutes. Add chicken and stir fry for 2 minutes. Add water, kecap manis and lemongrass and cook, uncovered, stirring for 30 minutes until all liquid has evaporated. Transfer to baking dish and grill under broiler for 5 minutes. Serve with rice.