Whisk together sugar, cornstarch, and salt in a medium saucepan. Stir in water. Bring to a boil over medium heat. Cook, whisking constantly, 1 minute; stir in lemon juice. Cook, whisking constantly, until mixture boils and thickens slightly. Remove from heat. Gradually stir about one-fourth of hot mixture into egg yolks; whisk into remaining hot mixture. Return to heat, and cook, whisking constantly, 3 minutes. Remove from heat. Stir in lemon rind. Cool completely. Cover and chill thoroughly.
Tip: To quickly chill Lemon Curd, place saucepan in a large bowl of ice water for 5 minutes or until completely chilled, stirring often.