Heat the caster sugar, lemon zest and wine in a heavy-based saucepan over low heat to simmering point, stirring to dissolve the sugar. Add the nectarines; the liquid must cover them so add a little more wine if necessary. Cover with a cartouche (round of baking paper) and a small plate. Poach the nectarines briefly, just enough to loosen the skins – the exact cooking time d