Preheat oven to 325 degrees F. Generously grease and flour ten 3 3/4- to 4-inch fluted individual tube pans or one 10-inch fluted tube pan. Remove 2 tsp. zest and squeeze juice from orange. Set juice aside for glaze.
In a large bowl combine orange zest and next six ingredients (through vanilla). Stir in next five ingredients (through salt) until combined.
Sprinkle about 1 Tbsp. pecans in bottom of each prepared individual pan and top with about 1/3 cup batter. Or sprinkle all of the pecans in 10-inch pan and top with all of the batter. Bake 30 to 35 minutes for mini cakes, 45 to 50 minutes for 10-inch cake, or until a wooden skewer comes out clean. Cool on a wire rack 10 minutes for mini cakes or 20 minutes for large cake. Remove from pan(s); cool completely on wire rack.
Meanwhile, for glaze, in a medium bowl stir together powdered sugar and enough of the orange juice (3 to 4 tsp.) to reach drizzling consistency.
Drizzle cake(s) with glaze and, if desired, sprinkle with additional pumpkin pie spice.