Cake: Grease bottom of 15 x 10 x 1-inch jellyroll pan with vegetable oil. Line
bottom of pan with wax paper. Grease paper with oil.
Sift together flour, baking powder and salt.
Beat eggs in deep bowl with rotary beater until foamy. Beat in sugar gradually
and beat until thick as cream. Add vanilla extract. Sift in a little flour at a
time, folding in lightly. Turn into prepared pan.
Bake at 375 degrees F or until cake springs back when touched, about 13 to 15
Loosen edges of cake from pan. Turn out on tea towel that has been spread with
confectioners' sugar. Remove wax paper at once. Roll cake gently with tea towel
in it. Cool.
Lemonade Filling: Add enough water to lemonade concentrate to make 1 1/2 cups.
Mix cornstarch, flour and sugar thoroughly in saucepan. Stir in lemon and water
mixture. Stir constantly. Cook until mixture is smooth and comes to a boil. Boil
1 minute. Remove from heat.
Beat a little of the hot mixture into egg yolks which have been slightly beaten.
Beat back into hot mixture. Return to heat and boil for 1 minute. Add butter and
Unroll the jellyroll. Fill roll and roll up again.