You will need :
125g of sugar
75g of flour
The zest of a lemon
30g of melted butter
First of all, separate the 5 egg whites and yolks.
Add sugar to the yolks and then whisk until the mixture whitens in color.
Add the flour.
And cooled, melted butter.
Beat the egg whites until they form stiff, white peaks.
Fold the egg whites into the mixture. Butter a sheet of parchment paper.
Then pour in the batter.
Spread it evenly.
Bake them for 7 minutes in the oven preheated to 240°C or 460°F. Take the cake out of the oven and let it cool under a clean tea-towel.