Answer: While there are three different reasons given for why we cover our challa
while reciting kiddush, some argue that not all of these reasons
necessarily apply to covering cake, too.
Tosafos (Pesachim 100b) writes that one reason for covering the challa
is to highlight the importance of kiddush. In the times of the Gemara
they would wait until after kiddush to bring in the food, though now we
simply cover the challa instead. Additionally, the covering serves to
remind us of the man that fell between layers of dew to
preserve it. The
Piskei Teshuvos (271:n193) points out that both these reasons apply
specifically to challa rather than cake. R’
Mordechai Leib Winkler (Levushei Mordechai OC 1:46) adds that the table
would only be brought out on Friday night and not the following day for Shabbos
lunch. Thus, this reason wouldn’t apply to kiddush during the daytime.
The Aruch Hashulchan (OC 299:14), however, writes that the
main reason why we cover the challa is so as not to embarrass it.
The
Rosh (Pesachim 10:3) and Tur (OC 271:9) quote the Gemara Yerushalmi that
teaches that as wheat is listed before wine in the shivas haminim,
the beracha for bread should ideally be recited before
the beracha for wine (See Mishna Berura 271:41). Based on this,
the Kitzur Shulchan Aruch (55:5) and R’ Winkler (ibid.) write that when one is
having cake at a kiddush, one would still need to cover it.
R’ Binyamin Zilber (Az Nidberu 2:8), however argues that this reason only
applies to challa which one could, if necessary, use for kiddush.
As one can’t use cake for kiddush, the acharonim never mentioned the necessity to cover cake.
Similarly, the Piskei Teshuvos (271:19) quotes various poskim
who write that covering cake isn’t as important as covering one’s challa.
In conclusion, if one is reciting kiddush and having some cake at
home, one should ideally cover the cake. At shuls where it isn’t easy to
do so, the minhag is not to.