Tahini Bucatini

Name: Tahini Bucatini
Ingredients: 1/2 cup tahini; 1/2 cup soy sauce; 2 tablespoons rice wine vinegar; 2 teaspoons toasted sesame oil; 3 cloves garlic, crushed; 1-inch pieces ginger, pealed and roughly chopped; 1/4 cup cilantro stems, roughly chopped; 1 tablespoon sriracha, or more to taste; 1/4 cup starchy pasta water or more if needed; 1 pound dried bucatini; Toasted sesame seeds, chili flakes, cilantro, and scallions for garnish