Bring all ingredients to room temperature before starting.

Grease the bottom of the cake pan and line it with parchment paper. I wrapped a damp towel around the outside of the pan to help the cake rise evenly.

Preheat the oven to 180°C.

Beat the eggs, sugar, and vanilla sugar with an electric mixer on high speed until the mixture becomes thick, pale, and fluffy.
For a stronger cardamom aroma, I added 2 drops of cardamom essence. This step is optional.

Sift the flour mixture over the batter and gently mix in one direction just until incorporated.

Pour the batter into the prepared pan. Insert a toothpick into the batter and gently swirl it around to remove any large air bubbles.

Bake in the middle rack of the preheated oven for about 45 minutes. Baking time may vary depending on your oven.

Optional Pistachio Topping:

Adding chopped pistachios on top of the cake is completely optional. Since this cake batter is relatively thin, pistachios may sink into the batter during baking if added at the beginning.

If you would like to add pistachios like I did, reserve 7 tablespoons of the batter and pour the remaining batter into the pan. Bake for about 35 minutes, or until you are almost sure the cake is baked.

Remove the pan from the oven and quickly spread the reserved batter over the cake in a very thin layer. Sprinkle the chopped pistachios over the batter and gently press them onto the batter with a spatula (very lightly).

I used 40 g of pistachio kernels, but you can adjust the amount according to your preference.