My son and I made cupcakes recently and decorated them with powdered sugar. Unfortunately, the powdered sugar melted into the cupcake. I added more powdered sugar on them and stored them in a tupperware container to transport them. The powdered sugar came off yet again (probably due to the moisture). Does anyone have any ideas how to keep powdered sugar on baked goods and how to store them and/or transport them so the powdered sugar remains intact? I've heard that adding a little cornstarch to the powdered sugar may help. Any tips would be greatly appreciated. Thank you!

Chances are your powder sugar already has cornstarch in it.

Can you store them in a cake box rather than an airtight container?

I doubt the container will matter much, I also find it very frustrating to dust something with icing sugar only for it to dissolve away into nothing.

The simplest answer to this is to not use regular icing sugar. There are "no melt" icing sugars for this sort of thing. Not sure where to get it though!