Preheat oven to 350 degrees.Butter the bottom and sides of a 9-by-13-inch baking pan. Put a long piece of parchment paper in the bottom of the pan, letting the parchment extend up the two short sides of the pan and overhang slightly on both ends. (This will make it easy to remove the bars from the pan after they have baked.) Butter the parchment.
In a large bowl, sift together flour, salt and pumpkin pie spice; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar together until light and fluffy; about 3 minutes. Add eggs, orange zest and vanilla; beating until well combined. Add the flour mixture and mix until combined. Fold in the cranberries and white chocolate. Batter will be thick.
Spread batter evenly into prepared pan and bake for about 20 to 25 minutes or until toothpick inserted into the middle comes out clean. Transfer to a wire rack and allow to cool completely.
In the bowl of a stand mixer fitted with the paddle attachment combine the cream cheese and butter until smooth. Add the powdered sugar, vanilla extract and orange zest and mix at low speed until combined. Spread over cooled cake. Garnish with dried cranberries, pistachios and white chocolate shavings.