Zest all of the skin off of the lemons into a small bowl.
Add cane sugar and use your hands to work the sugar into the zest mixture, rubbing it between your fingers.
Transfer this mixture into a larger pitcher or mason jar, and add tonic water.
To serve, fill 2 glasses with ice and strain the zest and tonic water mixture into both glasses, leaving room for the dragon fruit chunks (or mashed based on preference).
Divide the dragon fruit between the two cups to top it off!