Peel and core the apple. Retain the peeled apple skin to use later.
Fill water in a large bowl and add a tea spoon of salt. Add the peeled and cored apple as you work. *3
Remove the apples from the salty water and finely cut them.
Place the cut apple into a enamel coated pot and add the peeled skin as well. *4
Add the sugar over the apple and apple skin. Leave it for about 2 hours. The moisture in the apple will be extracted and you will see liquid at the bottom of the pot. *5
Place the pot over medium heat and add lemon juice.
Bring the apple and apple juice extract to boil. Skim off any scum on the surface with a little sieve.
Simmer it for 20 minutes or until thickened, stirring often with a wooden spoon. Once the colour of the apple skin comes off in the liquid, remove all apple skin before the liquids get thickened and discard them. *6
While the jam is hot, ladle the jam into a sterilised jar and place a lid tightly.
Cool it down in room temperature then refrigerate.
*1 Any variety of apple can be used. I used 4 small royal gala apples weighing 350g. Measure the apple weight because it determines the amount of sugar you need. *2 I calculated and added 40 % of apple weight. But the percentage of the sugar added is not necessarily the percentage of the sugar content of the jam made. If you have a sugar gauge it will be easier to calculate. I don't have one so this is how I calculated. I used 350g of apple. Generally speaking they contain 0.1 % sugar, 350 x 01 = 35. I added 40 % of apple weight sugar 140g. 140g +35 = 175g sugar content all together. The end product weight was about 290g. All sugar content (175g) divide by end product weight(290g) = 0.6. So this apple jam sugar content is 60%. To have 40 % sugar content, 350g (apple) + 140g(added sugar)=490g. 175g x 0.4 = 437.5g Let's say about 440g. So I needed to reduce the jam from 490g at begin with to 440g. I wanted to make close to 40% sugar content but I probably had to add pectin powder to get jelly texture. Because I reduced to 290g, the jam end up 60% sugar content. *3 *4 Around the apple skin and core it contains more pectin. For adding a little bit of colour and more pectin, I added the peeled skin and then removed it later. If you peeled as long strips, it is easier to remove. *5 Due to sugar's penetrating action, pectin inside the apple comes out with moisture. It can be left longer than 2 hours. I often prepare the apple a night before and leave at this stage over night. *6 Apple jam can be mashed if you like that kind of texture but I like the apple to retain its shape so I usually use firm flesh apple for that reason. *7 The length of preserving the jam is depends on the sugar content and the method you use to sterilise the jar. For this method and sugar content, it will keep about 3 weeks in the fridge.