Last night, I decided to bake a cake.
1 box chocolate cake mix, half a packet of instant pudding.
Replace the water with OJ, and bake in a bundt pan.
I’ve done this before and it turned out quite well.
Last night, not so much.
When I removed the cake from the oven, there was a ring, just outside the center hole, that had sunk. 
So, what causes this? I backed some of the extra batter as cupcakes, and they turned out well. They rose fine, baked through and didn’t sink.
So, what sunk my bundt cake?