Preheat oven to 165C (350F).
Butter loaf pan and line bottom with waxed paper.
Using food processor, pulse pistachios until finely ground, about 40 seconds. (Do not over process, or mixture will become paste.) Set aside.
In processor, at moderate speed, beat together butter and sugar until light and fluffy.
Add eggs one at a time, beating well after each addition, then add orange rind, sour cream & vanilla, mixing in. Scrape down.
Add the rest of the dry ingredients and nuts & mix until well combined.
Spread batter evenly in pan and bake until wooden skewer inserted in center of cake comes out clean, 35 to 40 minutes.
Cool in pan on rack 10 minutes, then run knife around cake to loosen and invert onto rack.
Drizzle with glaze made from icing sugar and the juice of the orange, decorate with candied orange peel and chopped pistachios.