Place tomato wedges in a shallow bowl. Sprinkle with sea salt flakes and black pepper. Set aside.
Heat oil in a 2-litre heavy-bottomed saucepan on medium-high heat. Add garlic, ginger and tomatoes. Sauté for 3-4 minutes until tomatoes are starting to soften.
Add stock, tamari, vinegar and white pepper. Adjust seasoning if needed. Bring to a rapid boil.
Prepare your cornstarch slurry by mixing cornstarch and water in a small bowl until it is smooth and lump free. Have your whisked eggs ready in a bowl.
Reduce heat to medium. Add the cornstarch slurry and stir and mix. Allow to cook for 2 minutes until the soup starts to thicken.
Using a wooden spoon stir the middle to create a vortex. Pour the egg in a thin stream down the center of this vortex, moving outward in a circular fashion. After you finish pouring, wait a few seconds for the egg to set and gently stir and mix thoroughly.
Simmer for another minute or two on medium-low heat until the soup is piping hot. Add spring onion and serve hot.