Finely zest the lemons, taking only the yellow outer peel and avoiding the bitter white pith. Place the zest in a bowl with the sugar. Rub the zest into the sugar with your fingertips for 1–2 minutes until the sugar feels damp and very fragrant. Let it sit for 10–15 minutes. Rubbing rather than simply mixing the zest into the sugar is what actually ruptures the peel's tiny oil glands, mechanically releasing those aromatic oils directly into the sugar without needing any heat.

Place the tamarind pulp in a heatproof bowl. Pour over the 700ml hot water at about 75–80°C. It should be hot enough to soften and extract the tamarind well, but not boiling. Cover and let it steep for 30 minutes. Mash and break up the pulp with a spoon or your hands once it cools enough to handle, then let it sit another 10–15 minutes. Strain through a sieve into a bowl, pressing firmly to extract as much flavor as possible. Discard the solids. You should have a strong tamarind base with a rich amber color and slightly cloudy look. Keeping the water genuinely below boiling, in that specific 75–80°C range, is what softens tamarind's dense pulp thoroughly enough to extract properly while protecting its flavour from the flatter, more cooked character a true boil would introduce.

Add the lemon juice to the lemon sugar and whisk until the sugar mostly dissolves. Pour in the strained tamarind extract and whisk again until fully combined. The lemon juice's own acidity helps dissolve the sugar while carrying the already-released lemon oils fully into the base, and combining that citrus foundation with the tamarind extract at this stage, before the final water is added, lets both concentrated flavours integrate fully.

Transfer everything to a large pitcher. Add the 1 liter of very cold water and stir well. Taste. If needed, add a little extra cold water to bring the total yield to about 2 liters and to adjust the balance to your liking. It should taste bright, tangy, and clearly tamarind-forward. This tasting checkpoint matters directly given how much tamarind pulp itself can vary in sharpness batch to batch — building in that deliberate adjustment stage accounts for that natural variability rather than assuming a fixed recipe always lands at the same balance.

Refrigerate for 20–30 minutes until fully cold. That resting period lets the lemon, tamarind, and sugar fully integrate together, producing a more unified flavour than serving the drink immediately after mixing.

Place a thin lemon wheel inside each glass. Fill with ice and pour in the tamarind lemonade. Serve immediately. Serving right after chilling, rather than letting the pitcher sit out, keeps the drink at its coldest and most refreshing right when it's poured.