Separate the whites from the yolks, set the yolks aside, and put the 6 whites in a big bowl with a pinch of salt.
With a mixer, using high speed, mix until you obtain a firm meringue (when you turn your whisk upside down, the peaks will hold), and set the meringue aside.
Take another bowl and mix the butter (which you have left out of the refrigerator for a few hours) and the sugar.
Add the yolks one by one and keep mixing until you have incorporated them. Only now, incorporate the milk, the brandy, the vanilla, and the lemon zest.
Add the flour little by little.
Once all these elements are incorporated into a soft batter, start adding the meringue.
Do not use the mixer to prevent the meringue from softening. Use a rubber spatula or a wooden spoon, little by little and with soft movements to also incorporate some air.
Use a 32 cm cake pan that has previously been buttered and floured. Add the batter to the cake mold and the small coin that you have previously wrapped in aluminum foil.
Bake in a preheated oven at 170 °C for 45 to 50 minutes.
Once out of the oven, let it cool and decorate with icing sugar on top.