In a large microwavable bowl, combine the sugar and eggs, whisking until smooth.
Then, stir in lemon juice, lemon zest, and the butter.
Microwave the lemon and egg mixture for 3-4 minutes in 45-second intervals, stirring between each interval until the mixture is thick.
What you're looking for is the lemon curd to be just thick enough to coat the back of a spoon.
Transfer the lemon curd to a bowl and cover with a layer of cling wrap, directly touching the curd.
This will keep the curd from forming a skin.
Allow for full cooling.
When cool, cover and refrigerate the lemon curd.
The curd will keep covered in the fridge for up to 3 weeks.
