Step 1

Add oxtail to a pot and cover completely with water.

Step 2

Cut the lemongrass in half, and using just the top, smash it to bruise, then add these tops to the pot. Keep the bottom half for later. Tear 5 kaffir lime leaves into chunks and add to the pot as well. Add 2 Tbsp of fish sauce and simmer the beef for 2 ½ hours. Skim off fat and scum that floats to the top as it cooks, and add water as needed to keep the beef covered.

Step 3

Once done, fish out lemongrass and lime leaves.

Step 4

Add onion and the diced tomato and simmer for another 30 mins; you want the tomatoes to dissolve into the soup.

Step 5

After the onions have softened and the tomatoes have disintegrated, check that the beef is fork tender. If not, keep it cooking longer until it is.

Step 6

Smash the remaining lemongrass bottoms to bruise and release aromatic juices, then cut into 2-inch pieces and add to the pot. Tear the remaining lime leaves into chunks, and add them to the pot along with the ginger. Simmer another 15-20 mins.  Note: The lemongrass, ginger and kaffir lime leaves pieces are for infusion only and are not meant to be eaten. Make sure you inform your guests or remove them before serving. You can also add them to a muslin or cheesecloth bag for easy removal.

Step 7

Taste and adjust seasoning with more salt or fish sauce. If you want, you can add the lime juice now, or you can serve a lime wedge on the side so people can squeeze in their own lime juice as well.

Step 8

When ready to serve, add wedges of tomatoes and cook just for a minute to soften slightly. Remove from heat and add chopped cilantro.

Step 9

Serve with a wedge of lime if you haven't added lime juice to the soup already. You can serve this with rice or have it on its own. Enjoy!