In a medium sized bowl, whisk together the flour, baking powder and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or with a hand mixer, beat together the butter, oil, and sugar for 3 minutes until light and fluffy.
Scrape down the sides of the bowl, and add in both eggs and the vanilla. Beat for an additional minute.
Add in half of the flour mixture and gently mix until no flour streaks remain. Then, gently mix in all of the buttermilk, followed by the remaining half of the flour mixture.