Separate the eggs and beat the yolks with the sugar until frothy. Then stir in the grated carrots. Mix the hazelnuts and almonds with the cornstarch and stir into the egg mixture. Add the cinnamon and lemon zest and some of the lemon juice. Beat the egg white with the pinch of salt until stiff and fold into the batter.
Bake the dough in a greased springform pan in a preheated oven at 150 degrees fan-assisted, 175 degrees top / bottom heat for 60 minutes on the middle rack.
After cooling, make a frosting from powdered sugar and the remaining lemon juice or water and decorate the cake.