First, peel and finely chop your pineapple; you can use your food processor in this step.
Combine the chopped pineapple, granulated sugar, and cinnamon stick in a medium saucepan and simmer for about 20 minutes on medium heat with the lid on. This step will help the pineapple and sugar cook in their own juices and dissolve the sugar.
In the meantime, mix the cold water and cornstarch and set aside.
After the pineapple mixture has softened and thickened, add the cornstarch with water to the pot and occasionally stir so it doesn't stick to the bottom of the pan. Stir well and simmer for a few minutes until the desired thickness. You should be able to see the bottom of the pot when you stir it with a spoon. See notes for more tips.
Remove from heat and let it cool.
