The dough is a bit stiff, but it will stretch to the size you need with pressure. If you’re finding it to be a huge pain, that the dough clearly wants to go to 8 inches but not 9, just go ahead and make the cake 8 inches round. It will be just as good of a cake; the layers might need a single extra minute to bake.
Ovens will vary, especially for such thin cookies, so keep an eye on the first round as of the 6-minute mark, checking in each minute after as it can brown very quickly, and then you’ll know how much time you need for the remaining ones.
This dough is easiest to roll/softest when it’s still a little warm; if yours has cooled quickly, I found that you could put each piece in the microwave for 5 to 7 seconds (only!) to get it a touch warmer again, without prematurely baking the cookie.
Go ahead and save all of those used pieces of parchment paper for the next step and beyond. We’re going to use them again.
