Prepare the Peach: Wash, peel and dice the peaches. In a small pan, add water, sugar, diced peaches, lemon zest or lemon juice and cornstarch. Stir to dissolve the cornstarch. Cover the pan.
Cook the Peach: In medium low heat, cook for 10- 15 minutes or until the peaches are soft and tender. Stir at least once then cover again and continue cooking. In the last 5 minutes, set the heat to low making sure not to burn the sugar. Cooking time could vary depending on how ripe the peaches that you are using, adjust cooking time as needed. If you are using a really ripe peach, check the peach at 10 minutes mark. The consistency will thicken as it cools down. You can increase the cornstarch to 1 tbsp if you want a thicker consistency, or if you prefer it sweeter you can add more sugar.
Cool and Store: Transfer in a bottle and let cool completely before storing in the refrigerator.