1Beat eggs for 5 minutes, gradually adding sugar. Stir in pumpkin and lemon juice and set aside. Combine and stir flour, baking powder, and spices. Fold into mixture. Spread on a greased and floured jelly roll pan and top with crushed walnuts. Bake at 375 for 15 minutes. Turn onto a clean tea towel sprinkled with powdered sugar. Start rolling at the narrow end, roll up in the tea towel and cool completely. Beat filling ingredients until smooth, unroll the cake, spread filling on cake and reroll. Wrap in plastic wrap and then aluminum foil. Refrigerate or freeze and use for a later date.