In a bowl put flour, salt and grated lemon peel. Mix the yeast with a teaspoon of sugar until liquefied, add a little warm milk and pour it over the flour. Mix the rest of the milk with the remaining sugar until it dissolves and pours over the flour. Beat the egg and egg white well and mix them with the yogurt, then add them to the flour. Knead all together, adding the oil little by little until you get a homogeneous dough. Cover the dough with a towel and leaven it in a warm place for approx. one hour.
Prepare the oil for frying in a pan over a suitable heat. Remove the dough from the bowl and spread it with the rolling pin in a sheet one centimeter thick. We cut the donuts with a glass and leave them to rise for another ten minutes covered with a towel.
Fry the donuts on the right heat on both sides until nicely browned, then take them out on paper towels and let them cool, then put them in powdered sugar and serve. I couldn't help but eat some that were so warm, and the dwarf asked for a double portion, so I can say that they were a success!