Whisk all ingredients together in a medium saucepan or double boiler
Continue to whisk and cook for about 10-15 minutes until the curd thickens and coats the back of a spoon. (About 180 degrees Fahrenheit)
Strain through mesh strainer and place in containers to refrigerate until ready to use.
Top with a pinch of zest just before serving if you like
Video
Notes
Using the erythritol produces a slightly different finished texture on the top- basically the way it dries. If you want to avoid the cracked top try covering the lemon curd with cling wrap or something similar.