01 - Combine blueberries, sugar, lemon juice, lemon zest, and water in a small saucepan. Cook over medium heat, stirring occasionally, until blueberries burst and sugar dissolves completely, approximately 5 minutes.
02 - Remove saucepan from heat and allow the mixture to cool for 10 minutes to room temperature.
03 - Transfer cooled mixture to a blender or food processor. Blend until completely smooth, ensuring no fruit chunks remain.
04 - Pour blended mixture through a fine-mesh sieve into a clean bowl, pressing with a spoon to extract liquid while removing skins and seeds for optimal texture.
05 - Transfer strained puree to a shallow freezer-safe container. Place in freezer for 4 hours, stirring vigorously with a fork every hour to break up ice crystals and ensure smooth consistency.
06 - Remove from freezer and let stand at room temperature for 5 to 10 minutes to soften slightly before scooping into serving bowls.