01 - Combine water and sugar in a small saucepan. Bring to a gentle simmer over medium heat, stirring constantly until sugar completely dissolves. Remove from heat immediately.
02 - Add fresh basil leaves to the hot syrup, pressing gently with a spoon to release essential oils. Cover and allow to steep for 10 minutes to extract maximum flavor.
03 - Pour the infused syrup through a fine mesh strainer into a clean mixing bowl. Discard the spent basil leaves.
04 - Add freshly squeezed pink grapefruit juice, grated zest, and optional lemon juice to the basil-infused syrup. Whisk thoroughly until fully incorporated.
05 - Cover the bowl and refrigerate for at least 1 hour until the mixture reaches 40°F throughout. This step is crucial for proper texture development.
06 - Transfer the chilled base to an ice cream maker. Churn according to manufacturer instructions, typically 20–25 minutes, until the mixture reaches soft-serve consistency.
07 - Move the churned sorbet to a freezer-safe container. Cover tightly and freeze for at least 3 hours until firm enough to scoop.
08 - Let the sorbet stand at room temperature for 5 minutes before scooping. Serve immediately in chilled bowls or glasses.