Step 1In a medium bowl, whisk together the flour, cinnamon and salt. Set aside.
Step 2In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using a hand mixer, beat together the butter, granulated sugar and orange zest until light and fluffy, 3 to 5 minutes. Reduce the speed to low and add the flour mixture in 3 batches, mixing until the dough just comes together in clumps. Stir in the pistachios and cranberries.
Step 3Gather and press the dough together, then divide it into 2 equal pieces. Using a sheet of plastic wrap or wax paper as an aid, form each piece of dough into a log about 11/2 inches in diameter. Chill, wrapped in plastic wrap, until very firm, at least 2 hours.
Step 4Place racks in the upper and lower thirds of the oven and heat the oven to 350 degrees.
Step 5Line 2 large baking sheets with parchment paper. Lightly brush egg over the outside of the log, then sprinkle with decorative sugar. Cut each log crosswise into one-fourth-inch thick slices (if the dough softens too much, freeze the dough briefly until firm enough again to slice). Place the cookies about one-half inch apart on lined baking sheets.
Step 6Bake the cookies until pale golden, about 15 minutes, rotating the sheets halfway. Carefully transfer the cookies to wire racks, using a slotted spatula, to cool completely.