Preheat the oven to 325°F. Grease and flour a 10-inch tube pan or two 9-by-5-inch loaf pans. (I also lined my pans with parchment, because it makes the cakes so easy to remove.)

In a medium bowl, whisk together the flour, baking powder, and salt.

In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and cream cheese, and beat on medium speed until soft and fluffy. Add the sugar, and continue to beat for about 2 minutes more, stopping once to scrape down the sides. Add the eggs one at a time, beating well after each addition. Beat in the vanilla. Reduce the mixer speed to low, and add the flour mixture in three doses, beating only until the flour is absorbed and scraping down the sides of the bowl as needed. Scrape the batter into the prepared pan or pans.

Bake for about 1 hour and 15 minutes (for a tube pan) or 55 to 60 minutes (for loaf pans), or until the cake is golden brown, pulling away from the sides of the pan, and a cake tester inserted into the center comes out clean. Transfer the cake to a wire rack, and cool completely before loosening the sides with a thin knife and removing the cake from the pan.