Preheat oven to 375 degrees F (190 degrees C).
Butter a jelly roll pan. Line it with buttered
foil or buttered parchment paper.
Beat the eggs until thick and lemon colored.
Gradually add 1 cup white sugar, beating
constantly. Stir in water and vanilla extract.
Fold in flour, baking powder, and salt. Pour
batter into tin.
Bake for 15 minutes. It should be springy to the
touch, and beginning to shrink away from the sides
of the pan.
Lay out a tea towel, and sprinkle it with
confectioners' sugar. Turn the jelly roll out on
the towel. Take off the paper or foil. Cut away
crusty edges. Roll the cake up in the towel, and
leave it to cool.