In a bowl, combine (sift) cake flour, sugar, baking powder, and salt. Add soft butter and 1/2 of milk/egg mixture. Blend together until a thick paste is formed. Add the remaining milk/egg mixture, and blend until smooth and lump free. Set aside.
In a skillet, prepare caramel sauce by melting butter and adding the brown sugar, blending together until smooth. Simmer for 10-15 minutes.
In a large baking pan, lay out pineapple slices, touching each other. Spoon out even amounts of caramel sauce over each pineapple slice. Pour cake mixture on top of caramelized pineapple slices. Bake in a large baking pan at 325 F for 30 minutes, turn and bake for an additional 15 minutes. Remove from oven and let cool.
Flip over baked cake onto a large platter, and cut into eight even pieces. Serve with whipped cream, or heated with a scoop of vanilla ice cream.
Most home bakers fail with upside-down cakes by pouring batter directly onto pooling, watery fruit juices, which prevents the crumb from bonding properly with the pan base. Achieving structural integrity requires precise management of the sugar-to-fat ratio during the initial creaming phase. Sifting the 14 ounces of cake flour removes dense aggregates, allowing the fine protein strands to trap leavening gases more uniformly. Mixing the batter in two distinct stages ensures the gluten network develops just enough strength to support the heavy fruit without turning rubbery.
Managing the Caramel Base
Simmering the brown sugar and butter for 10 to 15 minutes drives off excess moisture, thickening the liquid into a viscous syrup that will not liquefy the cake batter upon contact. Pouring this cooked caramel directly over the pineapple slices creates a dense thermal barrier. Bake the assembly at 325 degrees Fahrenheit for 30 minutes, then invert the pan while the caramel remains warm enough to release cleanly from the metal surface.
Fresh Versus Preserved Fruit Chemistry
Raw pineapple contains bromelain, a proteolytic enzyme that breaks down protein structures and can prevent proper setting if the fruit is applied completely raw. Cooking the fruit directly in the caramel denatures these enzymes through heat exposure. Preserved fruit contains no active enzymes and introduces significantly less surface water, altering how much moisture the surrounding batter must absorb during the baking process.