Halacha Yomis - Onions and Knives OU Kosher Halacha Yomis This column is dedicated in memory of: Rav Chaim Yisroel Belsky, zt'l Senior OU Kosher Halachic Consultant (1987-2016)

I cut a raw onion with a fleishig knife, but the knife was clean and had previously not been used for several days. Can I eat this onion with dairy or cook it in a dairy pot? No. Shulchan Aruch (Yoreh De’ah 96:1) explains that foods that have a sharp taste, such as raw onions, absorb more easily than other foods. The pressure of the knife combined with the sharp flavor of the onion causes the onion to absorb the meat flavor that is present in the knife. This is true even if the knife appears clean and had not been used in many days. Therefore, one may not eat this onion with dairy, nor may they cook the onion in a dairy pot. Moreover, if one did cook the onion in a dairy pot, a shailah should be asked as to whether the pot requires kashering.