Clean, wash and cut the rhubarb into pieces. Boil up sugar and 2 l water in a pot while stirring. Add rhubarb and simmer for about 30 minutes.
Pour the rhubarb through a sieve and collect the stock in a second pot. Squeeze the rhubarb residues in the sieve well with a ladle. Reduce the brew open to approx. 3⁄4 l - this takes 30-40 minutes depending on the size of the pot.
After 20 minutes add lemon juice to the rhubarb stock and cook along. Let the syrup cool down briefly.
Pour it still hot into a prepared clean bottle, close it tightly and let it cool down. Tastes good when filled up with cold mineral water or sparkling wine (mixing ratio: 2-3 tbsp. syrup to 300 ml liquid).