In a small bowl, mix walnuts, brown sugar, butter and cinnamon.
Place egg whites in a large bowl; let stand at room temperature 30 minutes. Preheat oven to 350°. Grease and flour a 10-in. fluted tube pan.
In a large bowl, cream butter and sugar until light and fluffy. Gradually add egg yolks. Beat in vanilla. In another bowl, whisk flour, baking powder, baking soda and salt; add to creamed mixture alternately with sour cream, beating well after each addition.
With clean beaters, beat egg whites on medium speed until stiff peaks form. Fold into batter.
Pour half of the batter into prepared pan; sprinkle with walnut mixture. Pour in remaining batter. Bake 45-55 minutes or until a toothpick inserted in center comes out clean. Cool 10 minutes before removing from pan to a wire rack to cool completely. Dust with confectioners' sugar. Yield: 12 servings.