Preheat the oven to 350 degrees. Butter and flour a 10-inch tube pan. Line a baking sheet with aluminum foil and place prepared tube pan on top; set aside.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside,
In the bowl of an electric mixer, cream butter and sugar until light and fluffy, 3-4 minutes. Add in lemon zest. Beat in eggs one at a time, scraping bowl down between additions and mixing well.
In a large measuring cup, combine vanilla, buttermilk, and vegetable oil. In three additions, add the flour and buttermilk mixtures, ending with the dry ingredients. Mix only until incorporated. Pour into prepared pan.
Bake for 50-55 minutes, until a tester comes out clean. Cool completely on wire rack before serving.