2) In a large mixing bowl, cream the butter and sugar together. Add the sour cream and mix until incorporated.
3) Sift the bicarbonate of soda and flour together in a separate bowl. Add to the creamed mixture alternating with the eggs, one at a time. Add the vanilla.
4) Pour the mixture into the prepared loaf tin. Bake for 40 minutes to 1 hour or until a cocktail stick inserted into the centre of the cake comes out clean.