Shulchan Aruch (Yoreh De’ah 120:4) writes that a stove-top grate does not need tevilah. The Aruch Hashulchan (Yoreh De’ah 120:32) explains that the mitzvah of tevilah only applies to utensils that come into direct contact with food. Since the grate does not come in contact with the food, it does not require tevilah.
Rav Shlomo Zalman Auerbach zt”l (see Sefer Tevilas Keilimpg. 55) maintained that a metal pitcher used to hold plastic pouches of milk does not require tevilah, because the plastic pouch is used to transport the milk and is therefore considered a separate container.
However, if one lines a metal pitcher with plastic, the plastic is not considered a separate entity since it serves only as a liner. In such an instance, the pitcher would require tevilah with a bracha.
Similarly, Rav Schachter, Shlita said, a glass plate requires tevilah even if the cookies are served on a doily or foil. The doily or foil is used for decorative purposes and is not treated as a separate entity. In contrast, formishloach manos, one may place packaged food, such as a box of cookies or a bottle of wine, on a plate that has not been toveled.
In this instance, the wrapping is a package and therefore we view the food as being stored in the package and not as being served on the tray. A note should be included to the recipient that the plate has not been toveled.
Use common sense and be a mench. Whenever you give someone something which in normal usage would requuire toiveling the recipient needs to know if it has been toiveled or not. This should be standard practice not just with Shaloch Manos but with any appplicable gift.
What about a non-packaged food on a porcelain or glass plate? Stores sell nash prepackaged in glass containers.