Place a double boiler set up on medium to medium low heat with water at a simmer.

Zest lemons for 2 teaspoons zest (about 2).

Juice lemons (about 6) for 3/4 cup.

Place on medium-high heat just until it comes to a boil.

While the lemon juice is heating, separate and whisk eggs in a medium size bowl, slowly add the sweetener while whisking.

Add the salt.

Remove the lemon juice from the stove, and very slowly add it to the eggs, continually whisking.

Transfer the eggs to the pot and place on the double boiler on medium heat. Continue to whisk until it thickens.

Remove from heat and add butter, stir until butter is melted and incorporated.

Cover with plastic wrap directly on top of the curd to prevent a “skin” from forming.

Cool rapidly and immediately, preferably with an ice bath.

Refrigerate for up to a week.