If you don’t have a 12-inch cast iron, you can surely use a 10-inch cast iron skillet or a 10-inch cake pan. If you use a 10-inch cast iron skillet you may have a bit of batter leftover and the cake part will be thicker. No biggie! If you use a 10-inch cake pan, you’ll need to do step #4 in a skillet and then pour the caramel mixture into the cake pan.