Please HELP! I have a cake that I'm making for my nephew for tomorrow. I'm using Seriouscakes' yellow cake recipe. I'm sure someone out there knows what I'm talking about. Anyway... I let it cool and it just didn't feel right when I was about to torte it and I fould out it has a "layer" inside the cake that feels like hard jelly. I know, it's gross! So I am wondering is it the cake flour? Or is it undercooked? Please someone help me! The birthday boy really wants yellow cake and it looks as if I'm going to be pulling an all-nighter! Thank you

Did you use cake flour? It's supposed to be A/P flour.

It could be your oven, this has happened to me before and it was my oven that was the problem. I have a commercial oven and I find if I bake too long during the day the oven gives trouble.
The temperature drops and it doesn't reignite so the cake is left in an oven with almost no heat left and when you check the cake thinking its finished it has those jelly parts. It hasn't happened in months but I have seen the jelly thing you described.
I don't know about the recipe because I have never used it but I find this only happens with yellow cakes.