In a large mixing bowl, cream the butter and sugar together. Add the sour cream and mix until incorporated. Sift the baking soda and flour together. Add to the creamed mixture alternating with eggs, beating in each egg 1 at a time. Add vanilla.
Pour the mixture into a greased and floured loaf pan. Bake for 40 minutes to 1 hour or until toothpick inserted into the center of the cake comes out clean.