Line the base of your spring form with baking parchment. Grease the sides with butter and dust with a little flour.
Preheat your oven to 190°C or 374°F top to bottom heat.
Peel the carrots, discard of the ends and finely grate them.
Separate the eggs into egg white and yolks.
Add the egg whites into a bowl with the sugar and salt and whisk until stiff.
In a separate bowl whisk together the egg yolks, vanilla essence, milk and lemon peel. Melt the butter and carefully add it to the mixture.
Combine the flour and baking powder in a bowl and sieve them into the egg yolk mixture. Sieving the flour will add air into the dough and make the cake more fluffy. Thoroughly mix the cake dough.
Now add the hazelnuts and grated carrots and mix with a spatula until completely combined.
Carefully fold the stiff egg white into the cake batter. You do not want to mix too much as this point, as we do not want the egg whites to deflate again.
Pour or spread the cake batter in the form and bake for about 30-35 minutes. To check if the cake is done, prick a skewer into the middle. If it comes out clean it is done.
Leave the cake the cool down in its form for 10 minutes. Then carefully loosen the edges by running a knife around the cake. Let the cake cool upside down to ensure that the surface will be nice and flat.