Preheat your oven to 180C
Sift the flour, baking powder and salt together
In a 9 inch pan, pour the melted butter and sprinkle the brown sugar on top of it making sure you get to the entire surface of the pan. Place the sliced pineapples over the butter and sugar
In a stand mixer fitted with the paddle attachment, cream together the sugar and butter for 3-5 minutes
Separate the eggs, add the vanilla to the egg yolk and pour the egg yolk vanilla mixture into the butter mixture
Mix them for a minute
Add flour and juice alternating between them (starting with the flour and ending with the flour) mix until just combined
Whip the egg whites for a good 5-7 minutes until it forms stiff peaks
Fold the egg whites gently into the cake batter
Pour over the pineapples
Bake for 40 min or until a toothpick comes out clean
Once cooled down completely, flip