Mix all the dry ingredients in a bowl. In another bowl, beat the eggs and sugar with a mixer into a fluffy foam, add the flour mixture, and beat again. Pour in the mineral water and vegetable oil, then fold in the walnuts at the end.

Pour the batter into a pan - it should be a large one, since the cake rises a lot.

Bake for 50-60 minutes in an oven preheated to 160-180°C. Check for doneness with a wooden skewer.

Let the finished cake cool. Enjoy!