• Preheat the oven to 350F. Grease 9" round cake pan with butter.

Topping

• Cook pineapple and sugar in 10" or bigger skillet over medium heat until pineapple is translucent and had light brown hue, around 15 minutes.
• Transfer the fruit and sugar liquid to a stainer set over a bowl.
• Return the strained juices to the skillet, let it simmer over medium heat until thickened. The mixture will start forming large bubbles and begins to darken, around 6 minutes.
• Turn off the heat, stir in the butter and vanilla and mix until the butter is completely melted.
• Pour the caramel mixture into prepared cake pan and set aside. Let the pineapple sit in the stainer until the batter is ready.

Batter

• Sift together flour, baking powder, and salt.
• Beat butter in a large bowl with an electric mixer until light and fluffy, then gradually beat in granulated sugar.
• Add one egg at a time, beating well after each addition. Beat in vanilla and rum.
• Add half of flour mixture and beat on low speed just until blended.
• Beat in pineapple juice, then add remaining flour mixture, beating just until blended. It is totally fine if the batter looks curdled.
• Working quickly, distribute drained pineapple in the cake pan in even layer, gently pressing the fruit into caramel.
• Spoon batter over pineapple topping and spread evenly.
• Bake cake in middle of oven until golden and a tester comes out clean, for about 35 to 45 minutes.
• Let cake stand for five minutes before inverting it on a plate/cake board. Keep the plate/cake board and the pan pressed together while inverting.
• Serve cake just warm or at room temperature with dollop of whipped cream (with lime zest, if you fancy lime).