Preheat oven to 325 degrees F. Grease and flour a 10 in tube pan and set aside.
In a mixing bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each one. Stir in vanilla. Mix in 1 cup of flour and the baking soda. Then, mix in 1/2 cup buttermilk. Mix in another cup of flour, followed by the remaining 1/2 cup buttermilk, and ending with the remaining cup of flour. Pour into prepared pan.
Bake at 325 degrees F for 70 to 80 minutes. Check for doneness using a toothpick inserted near the center. When it comes out clean, the cake is done. Cool in pan for 15 minutes before removing to a wire rack to cool completely.