1 can tuna in water – reserve 2 tablespoons tuna water from the can
1 small onion (very finely chopped)
2 large tomatoes (diced)
1 pound dry thin spaghetti or regular spaghetti
1/4 cup shiso leaves or basil (shredded, about 12 leaves)
nori sheet (shredded)
salt and pepper to taste
Put soy sauce, rice vinegar, sugar, olive oil, sesame oil and 2 tablespoons tuna water and whisk until sugar has dissolved.
Put onions, tomatoes and tuna in a bowl and pour sauce on top. Toss to coat evenly and refrigerate for at least 20 minutes.
Bring a large pot of water with salt (water should be salty to taste) and add spaghetti. Cook until al dente, according to directions on the package (about 6-7 minutes for thin spaghetti). Rinse under cold water and drain well.
Put spaghetti and sauce in a bowl and toss until coated evenly. Season with salt and pepper and serve topped with shiso leaves or basil and shredded nori.
This Japanese spaghetti will keep refrigerated for 2 days.