Start by cutting the beef into 6cm (2.4") chunks. Marinate the meat with the Bò Kho spices, garlic and 1 finely chopped onion for a minimum of 20 minutes.
To make the stock, bring a pot of water to a boil and add the bones in along with the peeled ginger. Let it simmer on a low-medium heat for at least 3 hours.
Meanwhile, char the remaining onions and ginger until the outside is black and the juices just start to bubble from the inside.
Remove the skin under running cool water, then add the aromatics into the stock along with the coconut water, rock sugar, salt and chicken bouillon powder. Let it simmer on a low heat as you work on the other ingredients.
Cut the lemongrass into 5cm (2") segments along their length and use a meat mallet or knife to crush them until they begin to split.
Heat up a wok on medium heat and add 5 tbsp oil in. When hot, throw in the lemongrass and tomato paste, then stir for 10 seconds.
Turn the heat up to high and pour in the marinated beef. Cook for 1-2 minutes or until all sides are seared.Tip: To avoid boiling the meat, divide and cook the beef, lemongrass and tomato paste in 2-3 batches.
Bring the heat up to high for the stock and add the cooked meat in.
Wash and peel the daikon and carrots, then cut them into 4cm (1.6") segments or to preference. Add them into the soup and let it simmer for another hour or until the meat is soft.Note: Keep the vegetables on the larger side as they will soften and break apart if too small and simmered for long.
Bring a pot of water to a boil and cook the tendons for 2 minutes to remove any odors. Drain, scrape off any impurities and add them into the stock to cook for another 3-5 minutes depending on your preferred texture.
Remove the tendons from the soup and cut into smaller segments, then leave aside in a bowl to eat with the stew.
Serve the Bò Kho hot with noodles, baguette, fresh herbs, chili and a squeeze of lemon juice!