Preheat oven to 325°F and generously grease/flour a 10-inch bundt pan.
In a large bowl, cream butter, shortening, and sugar for 4–5 minutes until light and fluffy.
Add eggs one at a time, mixing well after each.
In another bowl, combine flour, baking powder, and salt.
Add dry ingredients to creamed mixture in thirds, alternating with sour cream. Start and end with flour.
Stir in vanilla extract and scrape the bowl well.
Pour batter into prepared pan and smooth the top. Tap gently to remove air bubbles.
Bake for 1 hour 15–25 minutes, or until a toothpick comes out clean.
Let cool in pan for 10–15 minutes, then invert onto a wire rack and cool completely.