Preheat oven to 350 degrees. 

Place cast iron skillet with 4 tbsp butter in oven as it preheats. 

When butter is melted remove skillet from oven.  Sprinkle brown sugar evenly over melted butter and put back into oven until bubbly. Remove from oven and allow to cool slightly.

Remove pineapple rings from can.  Place one ring in center of skillet.  Arrange remaining rings around center ring to the edge of skillet.

Place maraschino cherry in the center of each pineapple ring, then set pan to the side.

Sift together flour, baking powder, and salt in medium bowl. Set aside.

In a large mixing bowl, cream together sugar and 8 tbsp melted butter until light and creamy.  Add the eggs and beat until smooth.

On low speed, incorporate a third of the flour mixture into the butter mixture. Add 1/2 cup of reserved pineapple juice, mix until smooth. Add 1/2 of the remaining flour, then 1/2 cup of pineapple juice.  Mix until smooth.  Add remaining flour mixture and mix until smooth.

Gently dollop cake batter over the pineapple rings in the skillet, being careful not to displace the fruit/sugar.  Smooth the batter with a spatula and gently tap on the counter to remove any air and settle the batter.

Bake for approximately 40 minutes, until it is a deep golden brown and springs back to the touch.

Cool cake for 10-15 minutes.  Invert cake plate over skillet; flip plate and skillet over so plate is now on the bottom.  Gently remove skillet from plate.

Serve warm or cool.