Whisk together the flour, baking powder, salt, and baking soda.
Using an electric stand mixer, cream the butter and sugar for about 5 minutes.
Mix in eggs one at a time.
Add the vanilla to the buttermilk.
Add flour mixture to butter mixture., alternating with buttermilk, beginning and ending with flour mixture.
Pour batter into Bundt pan and bake for 60 minutes.
Make butter sauce when you are getting ready to take cake out of the oven. Bring sugar, water, and butter to a low boil, stirring to dissolve sugar. Remove from heat and stir in vanilla.
After cake is removed from oven, poke holes in the top and pour the butter mixture down into holes. Let cake cool for about 10 minutes and then remove from pan. Don't let it cool much longer before removing from pan or it will stick.