1. Add the eggs together with the sugar and lemon juice to a heatproof bowl and place on a pot with simmering water. Heat up the mixture while stirring constantly until it starts to thicken and looks more or less like a pudding – takes about 8-10 minutes. The mix should reach a temperature of about 75°C (167°F).

2. Take off the heat and press through a fine-mesh sieve instantly. Add the lemon zest and the butter in small pieces and mix until the butter has melted completely and you have a nice and smooth lemon curd. Cover with a piece of plastic wrap directly on the surface of the curd (to avoid the development of skin) and let cool down. You can also fill it into glass jars directly and close them. The curd can be stored for up to a week in the fridge.