Cover 2 cups of raw tiger nuts with water by 1in / 2.5cm and soak for 24 hours. Drain and rinse.
In two batches, blend the tiger nuts with 4½ cups of cold water, ¼ teaspoon of ground cinnamon, and 1 teaspoon of lemon zest until well combined.
Strain through a sieve, pressing the pulp to extract all the liquid. Stir in 2 tablespoons of sugar until dissolved and refrigerate for at least 4 hours.
