Mix 1 tablespoon tahini, 2 teaspoons low-sodium soy sauce and 1 teaspoon each rice vinegar, sugar and water until smooth. Cook 1 pound spinach (not baby) in salted water until tender, 1 to 2 minutes. Plunge into a bowl of ice water, drain and squeeze dry. Toss with 1 teaspoon sesame oil and season with salt. Drizzle with the tahini sauce and toasted sesame seeds.