Cream butter, sugar, and orange zest until fluffy (about 3 minutes).
Whisk flour and cornstarch together in a separate bowl.
Gradually add dry ingredients to butter mixture until just combined.
Fold in chopped cranberries and pistachios.
Divide dough into 2 logs, wrap, and chill for 1 hour.
Slice into ¼-inch rounds, bake at 300°F (150°C) for 15–17 minutes.
Cool on rack before serving or storing.
