Peel the kiwis and place them in a large bowl with water and the juice of one lemon. Make sure the water covers the kiwis completely.  

Let them sit in the lemon-water mixture for 20'-30'.

Then, rinse them well so that all the sourness goes away, 3-4 times. 

Place the kiwis in a pot with the sugar and set them aside overnight. 

The following day all the juices will have come out. 

Boil until you can pierce them with a fork. They should be tender and crunchy at the same time.