Pre heat the oven to 180 ℃ / 160 ℃ fan assisted / Gas Mark 4
Lightly grease the cake tins with some of the butter
To make the sponge first, mix together in a mixing bowl the plain flour and baking powder.
Then cream the unsalted butter, vanilla extract and caster sugar, by whisking them in a bowl until they are a lighter coloured and fluffy.
Next add one egg at a time, whisking them completely in between.
Then add the pre-mixed plain flour and baking powder mixture plus the buttermilk into the mixing bowl. Whisk well until everything is combined.
Divide the cake batter evenly into the two cake tins.
Bake for around 30 minutes or until a skewer comes our of the cake clean.
Once cooked, place the sponges onto a wire rack to completely cool.