1In a Large bowl, combine the first seven ingredients. In another bowl, combine the eggs, pumpkin, buttermilk, oil and vanilla. Stir into dry ingredients just until moistened. Fold in pecans. Fill six greased or paper-lined jumbo muffin cups.
2In a small bowl, combine the brown sugar, pecans and flour; cut in butter until crumbly. sprinkle over batter.
3Bake at 375 for 25 - 30 minutes or until toothpick comes out clean. Let cool for 5 minutes then remove from pan.