Grate the apple and squeeze half lemon on it, mix to combine. This step will allow the apple to keep its color and prevent browning.
Add the blended pineapple to a pot along with the remainder of the ingredients, stir and bring it to a boil.
Once it boils, lower the heat to medium and let it cook until the pineapple jam looks shiny and taste caramelized, stirring from time to time especially at the end of the cooking time. this might take from 25 to 40 minutes, so be patient.
Another way of learning if your jam is properly cooked is if you run your spatula to the bottom of the pot and if you can see the jam separates.
Turn off the heat, put the jam into a clean and sterilized jar, and keep it in the fridge.
Lasts for up to 4 weeks in the fridge.