Add the apricots and measurement water to a saucepan, then cover and cook gently for about 15 minutes until soft. Leave to cool for 10–15 minutes.
Purée the apricots in a food processor or liquidizer with the lemon juice. Melt the butter in a large bowl set over a saucepan of simmering water. Add the apricot purée and sugar, then strain in the eggs and mix together. Cook for 40–50 minutes, stirring from time to time until the sugar has dissolved and the mixture has thickened.
Stir in the liqueur, then ladle into warm, dry jars, filling to the very top. Cover with screw-top lids, or with waxed discs and cellophane tops secured with elastic bands. Label and leave to cool, then store in the refrigerator for up to 2 weeks.
To serve, this curd mingles perfectly with lightly whipped cream and crumbled meringues, for an easy pudding.