Melt the butter and let it cool down. Whisk eggs and sugar until fluffy.
Add the flour mixed with the baking powder, grated lemon zest, butter and cream to the egg whisk and stir to evenly beat.
Pour the batter into a small long pan covered with baking paper, about 25 × 35 centimeters. Bake the cake in the bottom of the oven for about 25 minutes. Let the cake cool on the baking paper on a baking rack.
Frosting: Mix butter with cream cheese, icing sugar and possibly freeze-dried raspberry powder. Spread the frosting over the cake. Place the cake in the fridge until the frosting has solidified. Cut the cake into 24 squares. Garnish with grated lemon zest, raspberries and mint.