Wash & peel ginger root. Slice into coins and add to a small saucepan. Wash both lemons and remove the peel from one and place into the pan. Squeeze the lemon juice into the pan. Add water and sugar as well. If using the cream of tartar, you can add it now. I use the cream of tartar if I want to keep the syrup for a few days. The cream of tartar helps keep the sugar from crystallizing. If you plan to use the syrup on the same day you make it, or even the next day, you can omit this ingredient.
Bring the pan to a gentle boil and stir gently until the sugar is dissolved. Once sugar is dissolved, remove from heat and allow the ginger and lemon to steep in the pan for about an hour.
Once cooled, pour contents of the pan into a jar through a fine-mesh sieve to just get the liquid from the pan. Store in the fridge until you are ready to use. The soda syrup will last for about a week in the fridge.
I like to use about 1 tbsp of syrup to about one cup of sparkling water, but adjust to your taste. Garnish with mint leaves for an added special touch.
Notes
You can get really creative with this recipe by adding 1/2 cup rhubarb, raspberries, blueberries or strawberries to the recipe. Simply add to the lemon, ginger, water and sugar mixture and bring to a gentle boil. Follow the rest of the instructions as listed above. You could also swap out the lemon juice for lime juice.