In a bowl, cream the butter and sugar until light and fluffy.
Add eggs one at a time, beating well after each addition.
Beat in vanilla extract.
In a separate bowl, mix together flour, baking powder, baking soda, and salt. Add to the creamed mixture alternately with buttermilk, beating well after each addition.
Pour the batter into a greased and floured 10-inch tube pan.
Bake at 350°F until a toothpick inserted in the center comes out clean, for about 55-70 minutes.
Cool the cake for 10 minutes, then run a knife around the edges and center of the pan. Invert the cake onto a rack placed over waxed paper.
For the butter sauce, combine sugar, butter, and water in a small saucepan. Cook over medium heat until butter is melted and sugar is dissolved. Remove from heat and stir in vanilla extract.
Poke holes in the top of the hot cake and pour ¼ cup of the butter sauce over the cake. Allow the sauce to be absorbed.
Enjoy!