1.5kg (3lb 5oz) sugar
1 tablespoon citric acid or tartaric acid
zest and juice of 8 medium lemons
4 cups boiding water
place sugar, citric or tartaric acid, lemon zest and boiling water in a large heatproof bowl. stir until sugar has dissolves, then add lemon juice. leave to stand overnight or until cool, then strain through a fine sieve.
pour into sterilised bottles and seal. the cordial can be used immediately