Preheat the oven to 180ºC/Fan 160ºC/Gas Mark 4 and prepare two deep sandwich tins. Those which I use for this recipe are 20cm rounds.
In your bowl, cream together the butter and caster sugar until it is pale, light and fluffy. This is one of the most important stages as it incorporates air into the mix which will result in a well-risen cake that is light and fluffy.
Add a quarter of the eggs into the mix with a tablespoon of flour, beating well. Continue adding the eggs and flour at the same ratio until the eggs have been fully incorporated into the mix.
Sieve the remaining flour and baking powder into the bowl. Add a pinch of salt and the vanilla extract. Then gently fold in the ingredients until it becomes smooth and all ingredients are blended well.
Divide the mixture equally between the two cake tins.
Bake in your pre-heated oven for around 25 minutes or until well risen and springy to the touch. Leave to cool slightly and then turn out onto a wire rack.
If using a cream filling, prepare whilst the cake is cooling.
Once the cake is completely cooled, spread the jam over the base of one sponge (and cream on the base of the second). Sandwich both layers together.
Sprinkle with some caster sugar or sifted icing sugar to finish.