What kind of bakery items do not get horribly affected by electricity going off when the item is still in oven?
On a different tack to those above you can stabilize your oven temperature by using heat absorbing materials such as brick and stone, which will absorb heat when the oven is on, then release it when the power goes out. It does mean for longer pre-heating times as it takes lots of energy to get the stone or brick up to temperature, however it could save your cakes. Just make sure to use fireplace brick and not regular, as regular can crack. Better yet, get a piece of scrap granite or marble, that way you can use it as a bread stone as well.