Get all your ingredients ready.
Melt butter in the top part of a double boiler and place over low heat.
Add sugar and stir until well blended.
Stir until mixture is light and creamy; do not allow it to get too hot.
Slowly add beaten eggs to the mixture and whip vigorously after each addition. Note: if you don't add it slowly and stir well, you will get clumps of eggs. Also, please make sure the mixture isn't too hot.
If you do get clumps of egg, don't worry you can strain them out later.
Stir the mixture for another 10 minutes over the stovetop, and it will start to thicken.
Add lemon juice and rind to curd and stir for another 5 minutes until it thickens. The consistency will be like a runny pudding.
Take off the stove and cool.
As the lemon curd cools, it will thicken nicely.
Pour into jar and place in the fridge once cooled. The Lemon Curd should last for about 1-2 weeks in the refrigerator.