This creamy, tangy curd keeps for 4 weeks and is a lovely addition to any dessert, particularly tarts and cheesecakes.
Peel, core and chop the apples into even pieces. Add to a saucepan. Zest the lemon into the same pan and add a splash of water. Place on a medium heat. Cook the apples gently until soft. Beat the apples to a puree using a wooden spoon.
In the meantime, juice the lemon (remove the pulp and pips by passing through a sieve) into a heatproof bowl. Add the sugar and butter. Set aside.
Beat the eggs into a separate bowl. Set aside.
Once the apples have pureed, pass through a sieve into the heatproof bowl with the butter and sugar. Place the bowl over a pan of simmering water. As soon as the butter has melted, add in the eggs and whisk.
The eggs will split if the mixture is too hot. If this happens, remove from the heat and keep whisking until smooth. You can check the temperature of the mixture using a sugar thermometer. It should be no higher that 60C.
Stir the mixture over a gentle heat, until thick and creamy – this will take around 10 minutes. The temperature should reach 82C.
Immediately pour the curd into sterilised jars and seal. Store in the fridge. The curd will keep for up to one month.