To Make Clear Lemon Jelly Filling: Mix sugar, cornstarch and salt in saucepan.
Stir in water gradually. Cook, stirring constantly, until mixture thickens and boils.
Boil and stir 1 minute. Remove from heat. Add lemon peel and butter.
Stir in lemon juice and food color; cool. If filling is too soft, refrigerate until set. Saliva can break down the filling; avoid tasting and douple dipping the spoon.
For the Cake: Preheat over to 375 degrees. Line a10-x-15-inch jelly roll pan with parchment paper, then grease and dust the parchment with flour, tapping our any excess.
Beat the eggs with a rotary beater until thick, about 4 minutes. Gradually beat in 1 cup sugar. Beat in all at once water and vanilla.
Sift together and beat in all at once flour, baking powder and salt. Beat just until smooth. Pour into prepared pan.
Bake in the preheated oven for 12 to 15 minutes.
Immediately turn upside down on a towel sprinkled with confectioners' sugar and remove parchment paper.
Spread cake at once with clear lemon jelly filling and roll up beginning at short end.