In a blender, combine fresh or thawed frozen blueberries, freshly squeezed lemon juice, monk fruit extract (or liquid stevia), and water. Blend on high until smooth, about 1-2 minutes.

Pour the smooth blueberry puree into an ice cream maker and churn according to manufacturer's instructions for about 20-25 minutes, until soft-serve consistency.

Transfer the churned sorbet into a covered, airtight container and freeze for at least 2 hours.

To serve, let the sorbet sit at room temperature for 5-10 minutes before scooping into bowls or cones.