Step 1

Preheat over to 350°F. Cut the pineapple quarters into 1/3" thick slices. Combine the sugar and the butter in a saucepan (or cast iron skillet - see note), over medium heat. When the butter has melted, stir to combine and continue stirring while the sauce simmers for 4 minutes. When the sugar and butter have combined and are bubbly, smooth and thick, remove from the heat. Pour the caramelized sugar mixture into a 9" round pan, spread with a spatula to coat the bottom of the pan. Arrange the pineapple slices on top of the caramel in a single layer.

Step 2

Whisk together the flours, baking powder, and salt. Beat the butter in a mixing bowl until light and fluffy. Gradually add the sugar, then the eggs, one at a time, beating well after each addition. Add the vanilla and half the flour mixture, beating on low speed just until blended. Add the pineapple juice, beat to combine and then add the rest of the flour, beating just until blended. (Batter may appear slightly curdled after adding the pineapple juice, it is fine.)

Step 3

Pour the batter over the pineapple slices and spread evenly. Bake the cake in the middle of the oven, until the top is a deep golden brown and a tester comes out clean, about 45-50 minutes. (The cake should not shake or wobble when removed from the oven.) Let the cake cool in the pan for 5 minutes, before inverting a plate over the pan and then inverting the cake onto the plate, keep the plate and pan firmly pressed together while turning. Replace any pineapple that might have stuck to the bottom of the pan. Serve warm or at room temperature. Enjoy!