Sift flour with baking powder, cinnamon and salt. Add nuts and orange peel and mix lightly. Beat eggs and stir in milk, oil and brown sugar. Make well in flour mixture and add egg mixture all at once. Mix very quickly, just until dry ingredients are moistened. Spoon into greased muffin cups, filling about 2/3 full. Bake at 375ºF. 12 to 15 minutes.