1 cup butter
2 1/2 cups white sugar
1 1/2 teaspoons vanilla extract
2 1/2 cups buttermilk
3 3/4 cups all-purpose flour
2 1/4 teaspoons baking powder
2 1/2 teaspoons baking soda
Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan. Sift together the flour, baking powder and baking soda. Set aside.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Beat in the flour mixture alternately with the buttermilk, mixing just until incorporated. Pour batter into prepared pan.
Bake in the preheated oven for 35 to 40 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool.