Marinate the tuna. Add the cubed tuna to a mixing bowl with the olive oil, soy sauce, sesame oil, lemon zest, ginger, and a small pinch of salt. Gently toss to combine, cover, and refrigerate while you prepare the pesto and pasta.

Make the pistachio pesto. Add the pistachios, basil, garlic, lemon juice, olive oil, and salt to a food processor. Blend until completely smooth, scraping down the sides as needed.

Cook the spaghetti. Bring a large pot of generously salted water to a boil. Cook the spaghetti until al dente according to package directions. Reserve some pasta cooking water before draining.

Toss with the pesto. Add the pistachio pesto to a large stainless steel mixing bowl. Add the hot spaghetti and toss vigorously, adding a splash of reserved pasta water at a time until the pesto becomes creamy and evenly coats the pasta.

Plate. Twirl the spaghetti onto each plate. For the nigiri-inspired presentation, shape it into a horizontal nest.

Finish and serve. Spoon the chilled tuna tartare over the pasta, finish with fresh chives, and serve immediately.