Streusel Coffee Cake

Preheat oven to 350 degrees. Grease 12-cup fluted baking pan; dust with flour. On waxed paper, combine baking powder, baking soda, salt, and 3 cups flour. In small bowl, combine pecans, brown sugar, cinnamon, and remaining 1 tablespoon flour. In large bowl, with mixer on medium speed, beat granulated sugar, butter, and 2 teaspoons vanilla until creamy. Beat in eggs 1 at a time. Alternately beat in flour mixture and sour cream, beginning and ending with flour mixture. Beat just until blended, occasionally scraping bowl with spatula. Spread 2 cups batter in bottom of prepared pan; sprinkle with half of nut mixture. Top with 2 cups batter; gently spread with spatula to cover nut mixture, being careful not to lift nut mixture out of place. Sprinkle batter with remaining nut mixture, then spread with remaining batter. Bake cake 55 to 60 minutes or until toothpick inserted in center comes out clean. Cool cake in pan on rack 10 minutes. With small spatula, loosen cake from pan. Invert cake onto rack; remove pan and cool completely.(Wrapped cake can be stored at room temperature up to 2 days.) Prepare glaze: In small bowl, stir confectioners' sugar, milk, and 1/2 teaspoon vanilla until smooth. Transfer cake to cake plate; with spoon, drizzle glaze over cake. Let glaze set, about 15 minutes, before serving.