Preheat oven to 375°.
In a large bowl, combine flour, brown sugar, cinnamon and baking powder.
In a separate bowl add the beaten eggs, orange juice and oil; stir to combine.
Blend the wet ingredients into the dry ingredients, mixing just until moistened (batter will be somewhat lumpy).
Fold in cranberries, orange zest (if using) and nuts.
Lightly grease a 12-cup muffin tin or place 12 paper cups in each section.
Fill each section about ¾ full with the batter (cups will be almost full). Bake until golden brown, 20 minutes, or until an inserted toothpick comes out clean or with dry crumbs.
Remove muffins from pan to cool on a wire rack.
Serve with cream cheese or luxurious mascarpone!