Preheat oven to 350°
Cream butter and sugar together in a medium mixing bowl.
Add eggs, one at a time, beating well after each one.
Add sweet potatoes and mix well.
In a separate large mixing bowl, combine flour and pumpkin pie spice.
Gradually add sweet potato mixture to flour mixture while beating.
Stir in coconut.
Spoon batter into a well greased bundt pan.
Bake for 65 minutes or until toothpick inserted comes out clean.
Cool for 15 minutes and then invert pan to remove cake.
Dust with optional powdered sugar.