1Preheat oven to 350°F. Spray 12-cup fluted tube pan with baking spray; set aside. Combine brown sugar, flour,oatmeal,nutmeg and cinnamon in small bowl. Cut in 1/2 cup of the butter with pastry blender or 2 knives until mixture resembles coarse crumbs. Stir in pecans; set aside.
Beat the remaining 1/4 cup butter, dry cake mix and spices in large bowl with electric mixer on medium speed until light and fluffy. Add eggs, 1 at a time, mixing well after each addition. Add sweet potato; beat 3 minutes, or until well blended.
Sprinkle 1/3 of the brown sugar mixture onto bottom of prepared pan; cover with 1/3 of the batter, spreading to form even layer in pan. Repeat layers 2 more times.
Bake 45 minutes, or until wooden pick inserted near center comes out clean. Cool in pan 15 minutes; remove from pan to wire rack. Cool completely. Dust with powdered sugar.