Preheat oven to 350ºF.
Grease cake pan very well. Set aside.
In a large bowl, combine flour, baking powder, and salt. Set aside.
In another bowl, combine pecans, cinnamon, and brown sugar. Set aside.
Place butter and sugar in a third bowl. and with an electric mixer, cream, or whisk together, until light and fluffy. Using a rubber spatula, fold in vanilla and eggs blending thoroughly.
Stir the sour cream together with the flour mixture, alternating a bit at a time, into the other ingredients.
Pour half the cake batter in the bottom of the greased bundt pan. Sprinkle in half the nut mixture and top with remaining cake batter. Smooth with rubber spatula. Sprinkle remaining nut mixture over the top.
Bake for 50 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool for 20 minutes before turning it out onto a rack or cake plate.