Bring the water to a boil, then remove from heat and let it cool slightly to about 95°C / 203°F. Add the black tea bags and steep for 3–4 minutes only, then remove the bags without squeezing to avoid bitterness.
While the tea is still hot, add the light brown sugar and stir until fully dissolved, then add the sliced peaches and lemon zest. Cover and let the mixture steep for 10–15 minutes so the residual heat gently extracts peach aroma and citrus oils without cooking the fruit.
Strain the tea through a fine-mesh sieve into a bowl or measuring jug, pressing very gently to release liquid without forcing fruit pulp through. Discard the solids and let the extract cool completely.
Pour the cooled peach tea extract into a large pitcher, add the ice-cold water, and stir gently until fully combined and clean.
Refrigerate for 1–2 hours until fully cold and the flavors are integrated.
Fill glasses with ice, pour over the peach iced tea, and garnish with fresh peach slices and a twist of lemon peel.
