Mix the yeast with the spoon of sugar and warm milk and leave for a while, until it becomes foamy. Then beat well with the yolks and 300 g of flour with a mixer. Add salt, vanilla sugar, lemon peel and the rest of the flour. Knead to be an elastic and raw dough. Allow it to stand for 30 minutes.
After the dough has grown, the fluffy donut dough spreads on a counter top with the flour of a thin finger. Cut the rounds with a special shape or a glass with thin edges. The dough for fluffy donuts is left on the tray after 10 minutes.
Heat the oil well and place the donuts in the hot oil and the heat is low. They come back with 2 forks and on the other side, and when they turn golden, they are removed on absorbent towels, lightly shaken and placed in a bowl and sprinkled with vanilla powdered sugar, while still hot.
These wonderful fluffy donuts are served with jam or simple sugar, powder.