Cut the passionfruit in half and remove the pulp.
Strain the pulp trough a fine sieve set over a bowl. Press out all the juice and keep the seeds separately if you want to add them later.
Grate the rind of the lemons in a bowl. Cut the lemons in half and squeeze out the juice.
Combine the passionfruit juice, lemon rind and lemon juice.
Beat the whole egg, egg yolks and sugar together in a pot.
Place on a low heat and keep whisking.
Once the sugar has dissolved add the juice and a pinch of salt.
Keep whisking until the curd starts to thicken up.
Add the butter cubes 2-3 at a time and whisk them into the curd. Once all the butter has been added check the thickness of the curd.
When the the mixture coats the back of a spoon the curd is ready.
Strain the curd through a fine sieve.
Pour the curd into jars and allow it to come to room temperature before sealing with a lid. Keep refrigerated for up to 4 weeks.