Step 1: Cook the udon for a few minutes after water is boiling, then remove and rinse it with cold water, drain and set aside.
Step 2: Cut the tomatoes in half, add a little of salt, and fry with the onions until fragrant, then set aside for later use.
Step 3: Pour the tomato sauce into the pot, add water and sauteed onions and tomatoes, then cook to form a soup base.
Step 4: In addition, blanch the shrimps and clams for later use.
Step 5: Put all the ingredients and the cooked udon into the soup base. After the soup base is boiled again, it is time to enjoy.