Wash the apples thoroughly and cut them into quarters.
In a large pot, add the apples and water. Bring to a boil over medium-high heat.
Once boiling, reduce the heat to low and cook until the apples are soft, about 30 minutes.
Strain the apples through a cheesecloth-lined colander. Do not press.
Weigh the juice and add 80% of that amount in sugar.
Add the juice and sugar to a large pot, and squeeze in the juice of half a lemon.
Cook over medium heat, skimming and stirring often.
Cook until the temperature reaches 226˚F (108˚C).
Transfer the jelly to a sterilized jar.
