Heat oven to 375°. Grease and flour a 15-1/2 X 10-1/2 inch jelly roll pan, or spray with cooking spray. Beat eggs until thick; add sugar, gradually, continuing to beat. Add water and vanilla; mix. Sift flour, baking powder and salt. Add all at once and beat until smooth. Pour into prepared pan. Bake about 12-15 minutes or until cake tests done. Do not overbake, it will be difficult to remove from pan and roll. Turn out on towel well-sprinkled with confectioners' sugar. Quickly, trim edges with a sharp knife, and roll up in towel. Cool, unroll and spread evenly with soft mayhaw jelly and roll again. Slice and serve plain, or garnish with whipped topping and fresh fruit.