http://revach.net/article.php?id=1477

Section: Halacha   Category: Tshuvos
Rav Shlomo Zalman Auerbach: Can You Warm Up Jelly Doughnuts on Shabbos?

Rav Shlomo Zalman Auerbach (Halichos Shlomo Chanukah 17:11) says you can warm up Sufganiyot on Shabbos (in a Halachicly prescribed manner of course) despite two issues that arise.

The first issues is that the Sufganiya was originally deep fried which has a Din of Bishul.  Therefore warming it up would be Tzli Achar Bishul.  To this Rav Shlomo Zalman says since it doesn't change the taste from a taste of something cooked to a taste off something roasted it is not Tzli Achar Bishul.

The second issue is the jelly inside which is liquidy.  Liquid items may not be warmed on Shabbos.  To this he answered that the jelly isn't considered liquid. It is part of the donut which is mostly dry.

Important Note: We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.