Preheat the oven to 180°C. Cut the pineapple into small pieces and drain them. Beat the eggs with the powdered sugar, then add the flour, baking powder and warm melted butter. Pour the batter into a buttered mold and cover with pineapple. Sprinkle with brown sugar. Bake in the oven for about 40 mins.
Pour the liquid cream into a bowl, add the mascarpone and icing sugar. Mix everything together, then whip into whipped cream with an electric mixer. Stir in 2 tbsp. grated lemon zest and chopped lemon balm leaves. Place in the fridge to serve this chilled whipped cream with the cake.