At least I got the white powder part right

So Billy is in town this weekend for a short visit. His birthday is on September 11 (not good planning on his part), but since he's here now, I decided to make a cake for our little get together last night. I decided to try something different and was making the All-Purpose Buttery Yellow Cake from America's Test Kitchen. It sounded good, and with that much butter, it couldn't be bad, right?

This recipe does use a lot of butter, about twice what I'm used to using in a cake, but I figure it's supposed to be buttery. Anyway, after letting the baked cake layers cool in their respective pans for 10 minutes, I turned them out. The bottom of each of the layers looked really weird. Translucent, almost. "Uh-oh," I thought and figured they didn't get fully cooked, so put them back in the oven for a couple of minutes.

Then I turned them out again. Still translucent. That's really weird. But since this recipe called for so much butter, I figured maybe some of it melted, sank to the lower part of the cake, and that's what I was seeing. So I frosted it and it waited for the party.

Then we ate it, and it tasted really weird. It was sweet, sure, but very dense. The texture was just all wrong. Very dense. Rubbery, almost. So it didn't go over well.

This afternoon it occurred to me that, once in the past, my baked goods weren't coming out right and weren't as fluffy as they should have been. It turned out the culprit was baking powder that was several years old. I replaced the half-used baking powder, and things started coming out right again. So I opened the cupboard to check the date on my baking powder container.

You know how baking powder (my brand, anyway) comes in those little cardboard cans with a plastic lid on top? It turns out I had two in the cupboard:

You know, from the top, or if you're in a hurry, those look pretty similar. From the side, not so much:

Um, oops.