Cream butter and sugar. Beat in egg. Sift dry ingredients together and add, alternately with buttermilk, to butter mixture. Pour into well-greased 9 x 13 pan. Top with blueberries. Mix sugar, flour, and spices. Cut butter into tablespoons and blend into dry ingredients with a pastry blender. Mixture should be crumbly. Sprinkle over blueberries. Bake at 350 degrees for 35 minutes.