Clean the rhubarb and chop it into 1-2 cm slices. Add the chopped rhubarb, redcurrants and sugar to a stainless steel or enameled pot. Toss to combine and let sit for 30 minutes.
Add the water and lemon juice and bring to a boil. When it boils, lower the temperature and simmer for 15 minutes.
Remove from the heat and pour the mixture through a fine mesh sieve into a clean bottle or jar. Discard cooked fruit bits.
Notes
The use of non-reactive cookware like stainless steel or enameled pans is recommended due to the high acidity of the ingredients of this recipe.The nutritional information is meant as a guideline only. Please notice that the calorie count is referred to the syrup alone and does not count any extra calories added by the beverage this syrup is added to, if different from plain water.