Preheat oven to 325 degrees F. Liberally grease and flour a standard 10 to 12-cup Bundt pan.
Make the Cake: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large mixing bowl, beat the butter and sugar on medium speed until light and fluffy, about 3 minutes. Add the eggs, two at a time, until thoroughly combined. Add the vanilla extract and beat to combine.
Reduce the mixer speed to low and add the flour mixture in three parts, alternating with the buttermilk in two parts, beginning and ending with the flour. After each addition, mix until just barely blended and stop and scrape the bowl. Stop the mixer before the last of the flour has been incorporated and complete the blending by hand with a rubber spatula.
Scrape the batter into the prepared Bundt pan and bake until a toothpick inserted halfway between the edge and center comes out clean, 45 to 55 minutes.
Make the Butter Sauce: When the cake comes out of the oven, begin making the butter sauce. Place the butter, sugar, and water in a saucepan and warm over medium-low heat until the butter is completely melted and the sugar is dissolved. Do not allow the mixture to boil. Remove from the heat and stir in the vanilla extract.
Using a skewer, poke holes all over the top of the cake. Very slowly pour the glaze all over the cake, allowing time for it to soak in before pouring more. Allow the cake to cool completely in the pan, then invert onto a serving plate.