Buttery Lemon Spread
Wash the jars in hot soapy water, rinse well and put in a low oven to dry and become warm.
Put the lemon zest, juice, sugar and butter in a large heatproof bowl.
Place over a pan of simmering (not boiling) water and stir to dissolve the sugar.
Stir in the eggs and continue stirring for 15-20 minutes, until the mixture thickens enough to coat the back of a wooden spoon. Do not overcook, as the mixture will thicken more as it cools.
Pour into warm sterilised jars, cover with waxed discs and leave until cold before sealing tightly with cellophane covers or lids. Store in a cool place and use within 1 month