01 - Combine sugar and water in a small saucepan. Heat over medium heat, stirring continuously until sugar completely dissolves. Remove from heat and allow to cool to room temperature.
02 - Whisk together cooled simple syrup, pink grapefruit juice, grapefruit zest, and lemon juice in a large bowl or measuring jug until thoroughly incorporated.
03 - Pour mixture into ice cream maker and churn according to manufacturer instructions until reaching soft-serve consistency, approximately 20-25 minutes.
04 - Transfer churned sorbet to freezer-safe container, cover tightly, and freeze for 4-6 hours or until completely firm.
05 - Scoop sorbet into chilled bowls or glasses. Place 2 fresh basil leaves atop each serving and serve immediately.