Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 10-inch tube or Bundt pan.

Make cake: Cream sugar and butter in a large bowl with an electric mixer on medium speed until light and fluffy. Mix in mashed sweet potatoes and vanilla until well blended. Add eggs, one at a time, mixing well after each addition. Sift together flour, baking powder, cinnamon, baking soda, nutmeg, and salt in a separate bowl; beat into potato mixture on low speed until combined. Pour batter into the prepared pan.

Bake in the preheated oven until a toothpick inserted into the cake comes out clean, about 1 hour and 20 minutes. Cool cake for 20 minutes in the pan, then invert onto a serving plate.

Make glaze: Stir together confectioners’ sugar with 3 to 5 teaspoons orange juice in a small bowl until a drizzling consistency is reached.

Spoon glaze over warm cake and sprinkle with orange zest.