Preheat the oven to 350º F. In a mixing bowl, cream together the butter, brown sugar and sugar using an electric mixer. Beat in the eggs and vanilla extract. Gradually add the flour and baking powder, alternating with the buttermilk, mix by hand until incorporated.

Grease and flour a 10 inch tube pan (angel food cake pan) then pour the batter into the pan. Bake for 65-75 minutes or until a toothpick inserted in the center comes out clean. Allow the pound cake to cool in the pan (not inverted). Remove the cake from the pan and place on a large plate.

While the cake is cooling, prepare the glaze. In a medium pot over medium heat, bring the butter, brown sugar and milk to a boil and boil for 2 minutes. Remove from the heat and allow the mixture to cool to room temperature. Add in the vanilla extract, and whisk in the powdered sugar until the glaze is thick. Pour the glaze over the pound cake. Cut and serve.