This 15-Minute Cold Tuna and Tomato Somen Noodle is the noodle you need for summertime! With savory tuna, juicy tomatoes, and chilled umami-rich broth, you'd be happily slurping away even on a hot day.
You can prepare the following steps several hours before you serve. In a medium bowl, combine rice vinegar and sugar and whisk well.
Add canned tuna (without draining the oil) to the bowl and mix well with the seasonings.
Cut the tomato into 8 wedges, then cut each wedge into 3 pieces (about ½ inch (1.3 cm) cubes).
Add the tomato cubes into the bowl and season with freshly ground black pepper and sesame oil. Toss all together well and keep it chilled in the refrigerator.
Cut off the stem of the shiso leaves and roll them up from the stem side. Cut them into thin julienned strings.
Fluff them up with fingers and set them aside.
Make the noodle broth with 1 part mentsuyu and 3 parts cold water. Keep it chilled in the refrigerator.
When You Are Ready To Serve
Bring a large pot of water to a boil. No need to salt the water for somen noodles. Once boiling, add the noodles separately (like spaghetti noodles) and cook according to the package instructions, usually 1.5-2 minutes.
Keep stirring to make sure the noodles don't stick to each other. Control the heat so the water won't boil over.
Once the noodles are done, drain into the colander. Quickly run cold water over the noodles to let cool.
Once noodles are cool to touch, knead/rub the noodles between your hands several times under running water. This helps removing any excess oil from the noodles.
Drain well and serve onto individual plates.
Top the noodles with tuna and tomato mixture.
Pour the broth over the noodles and garnish it with shiso leaves.
If you have extra tuna and tomato mixture and broth (BEFORE serving), save them separately in airtight containers and store them in the refrigerator for 2-3 days. I recommend cooking noodles right before serving so they don't stick together.