Zest the citrus: Grate the peel of the lemons and limes using a fine grater (avoid the white bitter part).
Make the oleo-saccharum: Add all the zest into a bowl, add 1 cup sugar, gently massage it together until it turns wet and fragrant, let it sit for 2 hours.
Dissolve & steep: Add 1 cup boiling water, add a dash of pink salt + dash of citric acid, mix well, let it steep for 20 minutes.
Add fresh juice: Juice the lemons and limes you used earlier, add ½ cup lemon juice, ½ cup lime juice, mix.
Strain: Strain everything through a cheesecloth into a clean container.
To serve: Mix ½ cup citrus syrup with 2 cups carbonated water and ice (optional) and enjoy.
