Preheat oven to 160°C. Properly grease a Bundt tin Set aside.
In a standing mixer fitted with a paddle attachment, cream the butter and sugar until light and fluffy, about 2 minutes.
Add in the eggs, one at a time, beating between additions. Continue to beat until batter forms a pale yellow color. Mix in the vanilla extract.
Alternate folding in the premix and the buttermilk, mixing only until combined.
Pour batter evenly into prepared Bundt tin. Bake for 60 minutes, or until a knife inserted in the center of the cakes comes out clean. Allow to cool completely before frosting.