Step 1

Fill a large bowl with the eggs and egg yolks, lemon zest, sweetener, lemon juice, and salt.

Step 2

Place the bowl on top of a saucepan. Heat the water over low heat and start to whisk.

Step 3

Stir continually while the curd thickens, to prevent the mixture from sticking to the bottom of the pan. Take care to not let the mixture heat too quickly to prevent the eggs from cooking separately from the curd.

Step 4

Heat and whisk until the curd reaches 170 degrees Fahrenheit. If you don't have a cooking you can stop stirring and heating when the curd is a lumpy solid state. This should take 10-20 minutes.

Step 5

While the curd is still hot, fold the butter gently into the curd until it's completely melted.

Step 6

If desired, strain the curd to separate out any zest pieces or bits of egg that may have solidified.

Step 7

Let the curd cool to room temperature or place in the refrigerator to chill. If desired, place plastic wrap on the surface of the curd or cover with a bowl to prevent a 'surface skin' from forming.