Preheat oven to 325°F. Spray a 12-cup Angel Food Cake pan with non-stick cooking spray.
In a small bowl, mix 1 cup of pecans with 1 tablespoon of flour. Toss to coat. Set aside.
Whisk together the remaining 2 ¼ cups flour with the baking powder and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and 1 ⅓ cups sugar on medium speed until light and fluffy. Reduce speed to medium-low and the eggs one at a time, scraping the bowl in between each addition. Add the vanilla and mix to combine.
Reduce the speed to low and add the flour mixture in three additions, scraping down the bowl, as necessary. Add the sour cream and mix until combined.
Fold in the flour-coated pecans by hand until incorporated. Transfer batter the prepared pan and smooth the top. Sprinkle the batter with the remaining ¼ cup pecans and the remaining 1 tablespoon sugar.
Bake for 60-70 minutes, until a toothpick inserted in the center, comes out clean. Allow to cool in the pan on a cooling rack for 1 hour.
Run a thin knife along the edge of the pan to loosen the cake. Invert over the cooling rack and tap to release. Finally, invert the cake onto a serving dish, such that the pecan and sugar-sprinkled side is up.