Preheat oven to 350 degrees. In a small skillet, steam saute the onion in the orange juice until tender. Drain and set aside. Discard any remaining juice. Sift the flour with the soda and spices. Reserve. Cream the butter with the sugar and egg until light and fluffy. Add the pumpkin and vanilla. Mix well. Slowly add the dry ingredients. Stir in the onion and nuts until completely mixed. Drop by rounded teaspoonfuls 5 cm apart on a greased baking sheet. Bake for dozen to 15 minutes, until lightly browned around the edges. Cool on wire racks.