In a medium bowl, whisk egg yolks and brown sugar together. Add pineapple juice, flour, baking powder and salt. Mix until combined.
In the Speedy Chef, add egg whites and beat on gear I until stiff. Gently fold egg whites into the cake batter.
Place the 7 slices of pineapple on a paper towel to dry them.
Melt butter in the Universal Cookware Frypan 24cmon medium heat. Add brown sugar and keep on medium heat for 1 min. until the sugar starts melting and caramelizing.
Lay the pineapple slices flat neatly on the butter and sugar in the Frypan (use tongs, sugar is very hot). Allow to cook for approx. 1 min. without touching.
Pour cake mixture all over the pineapple slices, reduce heat to low, cover and allow to cook for approx. 15 min.
Remove the cover carefully but quickly to avoid allowing condensation to leak on the cake. Turn off heat and allow to stand for 5 min.
Unmold very carefully by flipping upside down on a serving plate (some hot juice from the bottom can leak when flipping the cake onto the serving plate).