Preheat oven to 180 degrees C. Grease and flour two 20x30cm pans. Sift together the flour, baking powder and bicarb 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 pans.
Bake in the preheated oven for 35 to 40 minutes or until a toothpick inserted into the centre of the cake comes out clean. Allow to cool.