Turn the oven to 180 deg C and preheat it for 10 minutes. While the oven preheats, prepare the cake batter.
In a big mixing bowl, combine sugar, vanilla sugar and butter. Whisk them together.
Add eggs- one at a time and whisk to make a smooth batter. ( Add one egg, whisk, then add the next, whisk. That way, whisk in all four eggs)
In a separate mixing bowl, combine flour, salt and baking powder.
Add this flour mix to the whisked sugar, butter and eggs.
Now add milk, lemon zest and lemon juice. Use a spatula to mix everything.
Grease and dusk the baking mould. Pour the batter. Tap it to even it and remove the air bubbles.
Bake at 180 deg C for about 50 minutes. After 50 minutes, insert a toothpick and check. If it comes out clean, the bake is baked. If you see batter stuck to the toothpick, bake for some more time. Do the toothpick test again and remove the cake from the oven when it is fully done.
Let the cake cool in the baking mould for about 15 minutes.
Then gently remove the cake and transfer it to a wire rack.
Prepare the frosting by combining powdered sugar with lemon juice.
Pour this evenly on the cake. Leave it like that for about 10 minutes.
Now, the cake is ready to be sliced.