Preheat the oven to 350 degrees. Grease the bottom of a 8.5 x 4.5 inch loaf pan or a 9 x 5-inch loaf pan and set it aside.
In a large bowl, mix the flour, sugar, baking powder, salt, and baking soda; stir in the butter until the mixture is crumbly. Then stir in the orange peel, orange juice, vanilla, and eggs, just until the batter comes together. Be careful not to overmix. Fold in the fresh cranberries and nuts if using.
Transfer the batter to the prepared baking pan. Bake until a wooden toothpick inserted in the middle comes out clean; about 50 minutes to 1 hour. Cool in the pan for 5 minutes before loosening the sides of the loaf from the pan with a knife. Transfer the loaf to a rack to cool completely before slicing.
Notes
If Baking Mini Loaves
Transfer the batter to three 5-3/4-in. x 3-in. x 2-in. loaf pans coated with butter or greased. Bake at 350º for 30-40 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pans to wire racks.