• Preheat oven to 350 degrees. Position a rack in the center of the oven.
• Add the butter to a 9-inch-round skillet (or baking pan). Place the pan inside of the pre-heated oven until melted, about 5 minutes.
• Remove the pan from the oven and add the brown sugar and rum; stir until mixed well and even.
• Arrange the pineapple slices evenly in the pan; place a cherry in the center of each one and fill the center and any other open space with either additional pineapple pieces or pecans.

For the cake:

• In a medium bowl, combine flour, baking powder and salt and whisk to combine.
• Using a stand mixer, beat the egg whites until fluffy; scrape into a clean bowl.
• Using the same mixing bowl, beat the egg yolks and sugar until thick and creamy; add the rum (or pineapple juice) and vanilla extract and mix well..
• Add the flour mixture and beat until well combined.
• Using a spatula, fold in the egg whites until just mixed in.
• Pour the batter over the fruit in the cake pan and smooth to the edges.
• Bake for 40 minutes until the cake is golden brown and a toothpick inserted into the center comes out clean.
• Place on a wire rack to cool for 10 minutes.
• Run a knife around the edges of the pan to loosen the cake. Place a serving plate over the pan and invert carefully allowing the cake to slide out of the pan.
• Serve warm or at room temperature; dollop with whipping cream if desired.