Start by peeling the pineapple and be careful to remove all the woody “eyes”. Cut it into small chunks and add to a large bowl.
Add the sugar and lemon juice and stir to dissolve the sugar. Halve the vanilla bean and scrape the seeds into the pineapple mixture. Add the pod to the mixture also.
Cover with plastic wrap and refrigerate for 1-2 hours.
Drain the liquid into a large, wide saucepan, preserving the pineapple and discarding the vanilla bean pod. Set the fruit aside.
Bring the pineapple liquid to a light boil over medium heat and cook for about 15 minutes, so any undissolved sugar melts and the liquid reduces a bit.
Add the diced pineapple to the liquid and simmer for 30 minutes, until the fruit is fully cooked and the mixture seems well assimilated.
Pour into the prepared jars, cover with a tight-fitting lid and let cool on the counter.
Then store in the fridge for up to 3 months.