In a large heavy saucepan, combine the sugar and cornstarch. Gradually whisk in water until smooth. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat; cook and stir 2 minutes longer. Remove from the heat.
Stir a small amount of hot mixture into eggs; return all to the pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer. Remove from the heat. Gently stir in lemon juice and vanilla.
Transfer to a large bowl. Cool to room temperature without stirring. Cover surface of mixture with waxed paper; refrigerate until cooled. Fold in whipped cream. Serve with fresh fruit.