Pour water in a soup pot. Let boil.
Add ginger, tomato, and onion. Let the water reboil
Add-in the lemongrass. Cover and boil for 5 to 8 minutes.
Gently slide-in the Tuna. Cover and cook for 12 to 15 minutes.
Add the fish cube and then stir. Cover and continue to cook between low to medium heat for 2 minutes.
Add the hot pepper leaves, scallions, long green pepper, and fish sauce. Stir and cook for 3 minutes.
Transfer to a serving plate. Serve with rice.
Share and enjoy!