1Heat oven to 350°F (325°F for dark or nonstick pan). Grease 8- or 9-cup fluted tube cake pan with shortening; lightly flour.
2Make cake mix as directed on box, using water, oil and eggs. Stir apple and 1/2 cup of the pecans into batter. Pour into pan.
3Bake 45 to 50 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; remove from pan to cooling rack. Cool completely, about 1 hour.
4In 2-quart saucepan, mix brown sugar, butter and milk. Heat to boiling over medium heat, stirring constantly with whisk. Boil 1 minute. Remove from heat; stir in vanilla. Gradually stir in powdered sugar until smooth. Stir gently 2 to 3 minutes or until slightly thickened. Immediately spoon glaze over top of cake, allowing some to drizzle down side. Top with remaining 1/2 cup pecans.