Sounds like too much batter. Is it spilling over the edges? If not then keep baking at ten minute intervals. Otherwise you might need to try again with less batter and use baking cores.
I would just let it go until the toothpick/cake taster comes out clean. The outside of the cake will get dark, but that can be trimmed and most of the cake will be perfectly fine. Next time for that size cake you might want to try metal "V" cores. But i would say it'll be close to twice the baking time to get a dry cake tester.
I'm sorry I forgot to mention I did use cores and baking strips. Ended up taking about an hour and a half but came out great! I am new to this and the lady at the cake supply store told me 325 for 50-55 mins! I knew that didn't sound right :/ Thank you guys for your help :)
So glad it worked for you! Yes, 325 takes longer but is the right temp to use for very large cakes like that.
Thanks! I am sure I will be posting many more questions in the future.