Mix all the ingredients for the syrup and heat them on a low stove. Stir until the sugar melts and you get a syrup. Then, get to work on the cake.
Whip the eggs with the sugar. After they form a fluffy cream, add the yoghurt, oil and dry ingredients. Stir and transfer the resulting mixture into a suitable tray or form, which you can butter beforehand.
Bake the sponge cake at 347°F (175 °C) for about 25 min., then cut it into squares and pour the cooled syrup over it. Leave it in the fridge for 1-2 hours before serving.