01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, baking powder, salt, and orange zest if using.
03 - In a separate bowl, whisk the eggs, vanilla extract, and melted butter until fully combined.
04 - Add wet ingredients to dry ingredients and stir until just combined. Fold in the cranberries and pistachios evenly.
05 - Divide the dough in half. Flour your hands and shape each portion into a log approximately 12 inches long and 2 inches wide. Place logs on the prepared baking sheet.
06 - Bake for 25 to 28 minutes until the logs are lightly golden and firm to the touch.
07 - Remove the logs and allow them to cool for 10 minutes. Lower oven temperature to 300°F.
08 - Transfer logs to a cutting board and, using a serrated knife, slice diagonally into 1/2-inch thick pieces.
09 - Arrange slices cut-side down on the baking sheet. Bake for 10 minutes, flip and bake an additional 8 to 10 minutes until dry and crisp.
10 - Allow biscotti to cool completely on a wire rack before storing in an airtight container.