1. Mix flour, pecans, cranberries, baking powder, baking soda, and salt.
2. In a large bowl, mix sugar, banana, vanilla, and eggs until well blended. Add butter and buttermilk; mix well.
3. Add flour mixture to bowl and stir until evenly moistened.
4. Butter and flour-dust a nonstick 10-inch decorative tube pan. Pour batter into pan.
5. Bake in a 350° oven until a long wood skewer, inserted in the thickest part, comes out clean, and cake pulls from pan sides, about 1 hour.
6. Cool cake in pan on a rack for 15 minutes. Lay a rack on top of pan. Holding pan and rack together, invert to release cake. Lift off pan. Serve cake warm or cool.