Bring the water and salt to a boil. Put 2 kinds of lettuce and tomyo and cook for 10~20 seconds, immediately soak in cold water and let them cool, then drain very well.
Just before eating, combine the drained vegetables and mayonaise and chopped ume(optional). Season with salt and pepper.
(※) For your reference→ https://cookpad.com/us/recipes/263876-marinated-vermicelli