Start oven at 400 degrees or moderately hot. Grease jelly roll pan, 15X10X1-inch. Line bottom of pan with wax paper. Put eggs, baking powder, and salt into mixer bowl. Beat 2 minutes at high speed or until light and lemon colored. Reduce speed to medium. Gradually add sugar and beat 3 minutes (mixture should be thick and very light colored). Reduce to lowest speed and add lemon juice, then flour, beating only until moistened. Pour into pan, bake 15 minutes.

After baking, carefully turn cake out onto clean tea towel (previously coated with confectioners sugar). Peel wax paper from bottom of cake. Trim all the crisp edges from cake. Lightly roll cake, towel, sugar and all--leave rolled up and cool for about 10 minutes on a cooling rack. Unroll cake. Carefully spread jam or jelly on cake. Reroll cake with jam in it. Wrap it in the towel to finish cooling. The final touch, just before serving, is to sprinkle confectioners sugar on each serving.