A simple sponge based on the yoghurt pot measure, which in Spain is 125ml. If you have bigger pots, you might need to add another egg and a bit more baking powder. I cooked this one last night, and it has already been quaffed by three teenage girls.  I might also have had a piece or two myself.

What you need:
1 pot of natural yoghurt
1 yoghurt pot of sunflower seed oil
2 yoghurt pots of sugar
3 yoghurt pots of plain flour
1 sachet of baking powder (16g)
3 eggs
the zest of a lemon or an orange

What you do:
Heat your oven to 180ºC and line a 23cm round cake tin (spring-form makes it easier to get the cake out later). Pour the yoghurt into a small bowl and set aside so you can use the pot to measure the other ingredients. Mix the sugar and egg yolks together in a large mixing bowl, then add the yoghurt and oil, stirring until smooth and glossy.  Sieve the flour and baking powder into the bowl pot by pot, stirring well but not over-beating.  Add the zest and then whip up your egg whites and fold gently into the mix. Bake for 30-40 minutes (every oven is different) and then allow to cool completely before the slicing and gobbling.

Serve with: tea