Marinate 1kg cubed beef with 1 litre Sparkling Water for 45 minutes to tenderize the meat.
Slice 6 serai sticks and garlic, mix all ingredients for grating: 1 large onion, 10 red onions, 1-inch ginger, ½ inch galangal, ½ inch turmeric, dried chilies, black pepper, cinnamon, white cardamom. Grate these ingredients until finely chopped.
Fry the grated mixture and tenderized meat in a wok or large pan over medium heat until fragrant and oil separates from the meat.
Add 1 litre of coconut milk, gula nisab, lime leaves, tamarind piece, salt to taste. Simmer the rendang on low heat for about 2-3 hours until the coconut milk thickens and the meat is well-cooked.
Meanwhile, steep hibiscus flowers in hot water for a refreshing drink.
Serve the rendang with the hibiscus tea infused with water squeezed from the petals, slices of longan, ice cubes, and finally, Sparkling Water (zero sweetener).
Adjust cooking time according to desired doneness. For drier rendang, let it simmer longer.