How to cook
Wash the oranges well. Cut them into pieces along with their peel and boil them for 20-30 minutes after the water had boiled.
Remove them from the heat and once they cool down, strain the juice. Add the sugar and place them on the hob again and at the end mix them with the citric acid.
While it's still hot, pour it into jars and close them tightly. Turn them periodically up and down with their lids until they have completely cooled.