Place pistachios in food processor and pulse 8–10 times. When chopped to the proper consistency, some pieces will be the size of small peas and some will be turned to a fine powder. Once the nuts reach this stage, set them aside.
In a large mixing bowl, or the bowl of a stand mixer fitted with paddle attachment, cream butter, oil, granulated sugar and powdered sugar until completely smooth. Add egg, orange zest, vanilla and salt and beat until fluffy.
Sift in flour and baking powder and stir gently until incorporated. Add chopped pistachios and mix until dough is completely and evenly blended. Transfer dough to a sheet of waxed paper and shape into a cylinder 2" in diameter. Roll up dough in waxed paper and refrigerate for at least 45 minutes until firm.
Preheat oven to 350 degrees, line a baking sheet with parchment paper and set aside. Remove cookie dough from refrigerator and remove waxed paper. Cut log into ½"-thick slices and place on prepared baking sheet.
Bake 10–12 minutes or just until cookies are set and no longer have a wet look on top. Remove from oven and allow to cool on baking sheet for 5 minutes before transferring to a wire rack to finish cooling.
One Last Thing
Dried cranberries are also delicious mixed in to these slice and bake cookies!