Preheat oven to 350.
Stir together 1/4 cup sugar, pecans, & cinnamon; sprinkle ½ mixture in a well-greased bundt pan. Beat butter at medium speed until creamy. Gradually add remaining 1 cup sugar, beat 5 to 7 minutes til light & fluffy. Add eggs, 1 at a time, beating just until yellow disappears. Add banana, sour cream & vanilla. Beat at low speed just until blended. Combine flour, powder, soda & salt. Fold into butter mixture. Pour ½ batter into prepared pan. Sprinkle with remaining pecan mixture. Top with remaining batter.
Bake for 45 minutes or until a wooden pick comes out clean.