Bring 200 ml of water with the sugar and a tablespoon of black tea to a boil. Put the pressed cardamom pods and the peeled lemon zest into the hot brew, steep and let cool down completely. Drain, add sherry and lemon juice and, depending on your taste, dilute with water. Normally you should start with an additional 300 milliliters.
Pour into a flat mold and freeze in the freezer. To serve, scrape off the ice shavings with a fork or spoon and serve in chilled dessert bowls or glasses.