Preheat oven to 350 degrees F. Cream butter and sugars until light and fluffy. Beat in egg yolks, then jam. Sift together flour and spices. Stir baking soda into buttermilk. Add flour mixture and buttermilk alternately to creamed mixture, then stir in dates and walnuts. Beat egg whites until stiff and fold into cake. Pour batter into greased and floured 10-inch tube pan; bake 50 to 60 minutes. Cool 10 minutes in pan, then invert on rack to finish cooling. Sprinkle with confectioners’ sugar.