Combine flour, baking soda, baking powder, cinnamon, nutmeg, and salt in medium bowl; beat sugar and butter with mixer on medium speed; then blend in pumpkin, egg, and vanilla until fully incorporated
Gradually mix in flour and dry ingredients; refrigerate dough for 3-4 hours
Preheat oven to 375F
Scoop dough into one inch balls; roll in powdered sugar; place dough balls on baking sheet; bake for 11-13 minutes
Remove cookies from baking sheets and place on cooling rack