How to Make It
Cook spaghetti in a large pot of boiling salted water until tender, 10 to 12 minutes.
While spaghetti cooks, combine tahini, ½ cup water, soy sauce, ginger, lemon juice, sesame oil, sugar, and ½ teaspoon salt in a food processor. Process until smooth, scraping down sides of bowl as needed.
Drain spaghetti and rinse under cold water. Toss with tahini sauce.
Heat vegetable oil in a medium skillet over medium-high. Add scallions and cook, stirring occasionally, until mostly golden, 2 to 3 minutes. Season with remaining ¼ teaspoon salt. Add scallions and vegetable oil to spaghetti and toss to combine. Top with sesame seeds.