Anyway, practice makes perfect and making Rainbow Cake doesn't seem as intimidating and daunting as when I first made it early this year for dear son's birthday.
These 2 cakes are both 7" round with 7 layers of colour - Red, Orange, Yellow, Green, Blue, Purple, Pink. Decided to stick to Whisk Kid's recipe since my test bake produced very good results; managed to adjust the recipe and buttercream frosting to fit this 7" configuration nicely. Had also adjusted the amount of ingredients so that the cake is much more tender than before, and the buttercream frosting less sweet so as to balance the sweetness of the cake.
For deco, I tried using M&Ms. Although it looked very pretty initially, the M&M would fade after a while due to condensation (initial storage in fridge) and the humidity :( Still have not found a way to manage this problem. So I guess I won't suggest using M&Ms for decoration in future unless I find a solution.
For packaging, as the cake is slightly taller than most cake boxes (commercial cake box is 5" tall, and the cake is about 5.5-6"), I improvised and used 2 boxes to make a taller box. Carrier is not a problem, since I've some nice plastic bags for cakes from Tokyo previously.
For those of you who are keen, please email me for order enquiry at email@example.com :)