Preheat oven to 350 degrees Fahrenheit
Grease a bundt pan thoroughly making sure every groove is greased
Ground the pistachios in a food processor
In a bowl mix the ground pistachios, flour, and baking powder. Set aside
In the bowl of a mixer, place the butter and sugar and mix using the paddle attachment for 3-4 minutes on medium-high speed
Scrape the sides of the bowl with a spatula
Add the vanilla and keep mixing
Add the eggs one a time beating well after each addition
Reduce the speed and slowly add the flour mixture in 3-4 batches
Finally, add the sour cream and mix
Pour the batter evenly in the bundt cake pan
Bake for 60-70 minutes or until a skewer inserted in the middle of the cake comes out clean
Remove from oven and let it cool in the pan for 15-20 minutes on a rack
Carefully invert the cake over the rack and let it cool completely