Add the sugar and lemon zest to a small bowl and massage the zest into the sugar until evenly incorporated
Add the diced strawberries, zest and sugar mixture, lemon juice, and still water to a small saucepan
Cook over medium low heat and simmer for 10-15 minutes until the strawberries have softened and broken down
Strain the cooked syrup to remove the strawberry solids, using a spatula or spoon to extract as much liquid as possible
Stir or whisk in the vanilla bean paste and move to refrigerator to cool
Once cooled, add 2-4 tablespoons of the syrup to an ice-filled glass and top with sparkling water
