Is there a
problem of bishul akum [the prohibtion of a goy cooking for a Jew - see its entry in the Talmudic Encyclopedia] in
a microwave oven?
One one hand,
we can say that a microwave is not the typical way we cook and was
thus not included in the original decree that prohibits bishul akum.
On the other hand, bishul akum is prohibited in order to prevent
closeness with goyim and the marriages that may result, so what does
it matter that the cooking is not done with fire and water but with
microwaves?
The poskim have a field day with this question. Among the permitters: Rav Asher Weiss Shlita in a super, highly recommended article in Oraisa [volume 18
page 159] and HaGaon Rav Nosson Geshtetner [Lihoros Nosson 7/64].
Rav Asher Bush in the Beis Yitzchak [Volume 33 page 143] and Rav Noach Isaac Oelbaum [Tshuvos Minchas Chen, I believe simman dalet] permit this bi-dieved.
In the sefer Shvus
Yitzchak on Gramma [page 61] Rav Elyashiv is strict about this matter and so it would appear from Rav Moshe [Ig"m 3/52]. And so ruled Rav Moshe Shternbuch Shlita in his Tshuvos Vi-hanhagos [Vol. 5/page 372] and Rav Vosner [Shevet Levi 8/185].
Now you have the sources - you can look them up and become all the wiser:-).
לזכות רחל בת גאולה לברכה והצלחה בכל מעשי ידיה.
