Preheat oven to 325F degrees.
Spray a 12-cup Angel Food Cake Pan with nonstick cooking spray.
In a small bowl, combine 1 cup chopped pecans with 1 tbsp. flour.
Stir well then set aside.
In a medium bowl, combine 2 1/4 cups all-purpose flour and 1 tsp. baking powder.
Set aside.
In the bowl of an electric mixer, cream the butter and sugar together until fluffy.
Slowly add in eggs (one at a time.)
Then stir in two teaspoons of vanilla extract.
Once combined, slowly add in flour mixture.
Then stir in sour cream.
Finally, stir in (by hand) floured pecans.
Batter will be thick.
Pour batter into prepared angel food cake pan.
Using the back of a spoon, spread out batter as evenly as possible.
Top batter with 1/4 cup chopped pecans and sprinkle with 1 tbsp. sugar.
Bake for about 55-65 minutes (until an inserted toothpick comes out clean.)
Allow to cool for an hour, then turn out onto a serving dish.