Boil udon according to the instruction. I personally used Sanuki udon pack. Drain it.

Chop tomatoes and mince ginger and spring onions.

Heat a little oil at medium fire and throw the condiment minces into the pan. Gradually you could smell the fragrance of spring onion and ginger. Now add your tomatoes into the pan. Stir fry and press the tomatoes with tour spatula to gain the nice tomato juice. When the tomatoes turn into the sauce-like mixture, add salt, a little sugar and a little umami flavouring.

Add 400ml hot water into the pan. Turn the highest heat on, boil the soup and then stop the fire after 5 min or when you smell the nice fragrance from the soup. Pour the soup into the bowl with udon. Serve the dish.