http://revach.net/article.php?id=3416

Section: Shabbos   Category: Likras Shabbos
Rav Shimshon Pincus: What Is Wrong With Baking A Cake On Shabbos?
On Shabbos there is a special mitzva to prepare good food for Shabbos.  Rav Shimshon Pincus asks how can eating food be the key to the Kedusha of Shabbos like Shofar is to Rosh HaShana and Lulav is to Yom Kippur?

He answers that eating food does not imbue you with Kedushas Shabbos.  Shabbos is a gift from Hashem, you just need to want it.  By preparing for it you show that you want it and are anxious for it to come, even on the first day of the week.

Why it is forbidden to bake a cake on Shabbos even if you are doing it in honor of Shabbos?  Rav Shimshon explains with a Mashal.  Imagine a married woman's parents, who she hasn't seen in a long time, come to visit.  They walk in and are greeted by the grandchildren, but their daughter is nowhere in sight.  They ask the children, who tell them that their mother is in the kitchen baking a cake in their honor.  "Who came for cake" asks her father?  We want to spend time with her.  Let's sit together and enjoy each other's company.

Cake is nice.  It provides a nice backdrop and shows that you hold your visitor in high esteem... but only if prepared before they come, not while they are there.  It is assur to read Divrei Chol on Shabbos.  Imagine the above scenario with the daughter or son sitting on the couch or in bed for a good portion of shabbos reading a novel or newspaper.  Not very flattering for the poor parents, is it?

Shabbos is a day that we are with Hashem.  The guest has arrived.  Everything is set.  Now is the time to spend precious time with our beloved guest.  We need to sit at the table and talk about things that interest Hashem, and not trivial matters that do not involve him or even repulse him.

Be a good host and the Shabbos Malka will come back week after week, with a smile and lots of special goodies for the wonderful family where she feels so comfortable and looks forward to spending her time.