1. Heat oven to 375 degree F. Coat a 12-cup muffin pan with nonstick cooking spray.
2. In a large bowl, whisk flour, baking powder, baking soda and salt. Set aside.
3. In another large bowl, beat butter and sugar until combined. Beat in eggs, banana and orange zest. Beat in flour mixture in 2 batches, alternating with half of the milk. Beat until just combined. Stir in raisins and nuts.
4. Spoon batter into muffin cups, about a generous 1/3 cup in each. Bake at 375 degree F for 20 minutes, or until a toothpick inserted into the center comes out clean. Let cool for about 5 minutes. Remove muffins from pan and cool on a wire rack.
5. Dust with confectioners sugar; serve.
6. Makes 12 muffins.