Beat the eggs with the sugar to a creamy mixture, add the oil.
Extinguish the baking soda in the yoghurt.
Make a well in the flour and add the eggs and yoghurt, add the lemon zest and knead a dough. Knead for about 10-15 min. until you get a smooth dough.
Leave the dough covered for about 15 min. to rest.
Put baking paper in an oven dish. Tear small bits of the dough and form balls.
Arrange them in the oven dish, smear with beaten egg yolk, sprinkle with sugar and put them in the oven.
Bake at 338°F (170 °C) until ready.