Whisk together first 3 ingredients in a medium saucepan; whisk in water until blended. Bring to a boil over medium heat; cook, whisking constantly, 2 minutes. Remove from heat; add butter, lemon rind, and lemon juice. Cook over medium heat, whisking constantly, 1 to 2 minutes or until slightly thickened. Remove from heat; stir in coconut. Place saucepan in a large bowl of ice water for about 5 minutes, whisking often until completely cool.