Preheat the oven to 355°F.
Divide the egg whites and yolks into separate bowls.
Add a pinch of salt into egg whites and beat them with the hand mixer until they form structures. Set aside.
Mix the powdered sugar and vanilla sugar in a medium bowl.
Sift the powdered and vanilla sugar mixture into the egg yolks and combine them together with the hand mixer until they form a sweet-tasting uniform liquid.
Pour ¼ cup of Limoncello into a glass, add fresh juice from one orange and stir them together.
Add ½ cup of milk and the Limoncello-orange juice mixture to the egg and sugar blend and combine them with the hand mixer.
In the same medium bowl, you mixed the sugars, combine 8 oz all-purpose flour and 3 teaspoons of baking powder.
Sift the flour&baking powder mixture into the yolks in parts, use the hand mixer to blend it. Do not add another part of the flour mixture until it is not blended with yolks, otherwise you will get clumps. Also after each part of the flour mixture, pour a bit of the ½ cup of sunflower oil.
Add the beaten egg whites in parts into the mixture, combine with a spatula.
Combine in 1 cup of chopped unsalted pistachios.
Divide the batter in ⅔ and ⅓ ratio into separate bowls (you can use the bowl, in which you had the egg whites).
Sift cocoa powder into the bowl with the smaller amount of dough and mix with the spatula.