Barb, double the recipe & you can use a cookie sheet...
Then cut two square layers from it for a layered cake.
SaraBeth Levine does that. She can get a 3-layer 8" cake out of one 12" x 18" sheet pan of batter. Two layers are full circles and the third layer is two semi-circles put together. With icing, she claims no one ever knows the difference. And she doesn't have to torte the top to even the layers.