Pineapple Upside-Down Cake

1 14 oz sliced pineapple in it's own juice (save the juice)
1/2 c. Brown sugar
2 T. Butter
2 T. Reserved pineapple juice from the canned pineapple

I have always used a 13" cast iron for my pineapple upside down cakes. Melt butter, add brown sugar and pineapple juice until sugar is dissolved. Turn off heat and arrange pineapple slices (I had three left, I ate one and pureed the other two and added them to the cake). I used blueberries instead of cherries in the middle of the pineapple slices.

Cake:
1/2 c canola oil
1/3 c white sugar
1/3 c brown sugar
3 eggs
2 slices pureed pineapple
1/2 c tapioca starch (bat nang in Asian section of grocery store)
1 c garbanzo bean flour
1 c coconut flour (Bob's Red Mill sells coconut flour, but I grind unsweetened dried coconut in a coffee grinder)
1/2 c. Reserved juice from canned pineapple
1 t baking soda
Pinch of salt

Cream together oil, sugar and eggs. Add the rest of the ingredients alternating wet and dry until well mixed. Spray edges of cast iron with spray oil. Pour the batter slowly over pineapple in cast iron. Bake at 350 for 30-40 minutes, cool 5 minutes, invert on serving platter.