Pour the cleaned of pits cornels in boiling water in an enameled container and cook for 4-5 minutes over low heat.
Remove from the heat and let them sit covered with a lid for 5-6 hours, then pass them through a plastic sieve, while also pouring their juice in. To the resulting solution, add the sugar, put it back on the heat and stir until dissolved.
Before removing the juice from the heat, add the citric acid.
Pour the boiling juice in bottles and close. Turn them upside down.