01 - Combine sugar and water in a small saucepan. Bring to a gentle boil, stirring constantly until sugar completely dissolves. Remove from heat immediately.
02 - Add fresh basil leaves to the hot syrup. Cover and let steep for 15 minutes to extract herbal flavors.
03 - Strain syrup through a fine mesh sieve, discarding used basil leaves. Allow syrup to cool completely to room temperature.
04 - In a large bowl, whisk together pink grapefruit juice, grapefruit zest, cooled basil syrup, lemon juice if using, and sea salt until fully incorporated.
05 - Refrigerate the mixture for at least 1 hour until thoroughly cold, ensuring optimal texture during churning.
06 - Pour chilled mixture into an ice cream maker. Churn according to manufacturer's instructions, typically 20-25 minutes, until mixture reaches a thick, slushy consistency.
07 - Transfer sorbet to a freezer-safe container. Cover tightly and freeze for minimum 3 hours until firm enough to scoop.
08 - Let sorbet sit at room temperature for 5 minutes before scooping. Garnish with fresh basil leaves if desired.