While we recommend robustly flavored whole-grain pasta to complement this creamy, nutty sauce, traditional pasta also was delicious. Short pasta such as orecchiette, farfalle and penne worked as well as flat noodles, like fettucine and tagliatelle. Adding the lemon zest to both the toasted walnuts and tahini sauce gave the dish a double layer of flavor. The ratio of yogurt to tahini was key to a full-flavored, creamy sauce. A bit of olive oil helped emulsification. Use a good-quality tahini made from toasted sesame seeds; if it’s salt-free, you may need to adjust the seasoning.