I make mine in a cast iron skillet too and it never comes out as crispy good as my mom's either! I have watched her make hers and do it the same way but it's never as good.
She melts the butter (lots) puts the sugar on top of the melted butter, pineapple on top of that and then the batter.
Maybe it has something to do with how hot the skillet is to start with?
It is nice that we are sharing the same issue. I will keep trying and you do too, and whoever figures it out can share the "secret". I watched my mom make "my" birthday cake many, many times. I swear you could have cut a piece of paper with the carmalized edge of the "top" of the cake after it was turned over!
My mother also used lots of butter (never saw her measure, but she put a couple sticks in), brown sugar (she used a two cup measure, which was filled to varying heights on different years). She put the pineapple rings around the edge of the bottom of the cast iron skillet and one in the middle. She put a maraschino cherry in the middle of each (stemless) and scattered a few chopped ones just outside the pineapple. She cut a few (this also varied over the years) in half and stood them up along the sides of the skillet.
She always made the cake mix from scratch, (this is where I really got lost), but she used the reserved pineapple juice with all its sugar, diluted with some water, instead of milk or water for the batter. Two eggs.
She always let it cool completely before she turned it over. She said that let the juices congeal. Oh, almost forgot: she always sort of pushed the pineapple slices down into the butter and sugar. That resulted in the pineapple almost being "clean" when you saw it after the cake was turned over.
My mother was all Irish. She wasn't much of a cook, but she could bake! Well she raised a family of 6 and none of us were hungry, so her cooking can't have been that bad.
People raved over her lemon meringue and pumpkin pies. We normally had home made biscuits, sourdough bread, cakes and pies to die for, and the whole extended family showed up when Marge was baking something. RIP mom. We always ate dinner in the kitchen together, until I left for the Navy.
