Sparky Lemon Curd

4 large egg yolks
1/2 cup sugar
1/2 cup fresh lemon juice (2 1/2 lemons)
3 Tbsp. butter
pinch of salt
2 tsp. finely shredded lemon zest

In top of double boiler, beat the yolks and sugar until well blended.
Stir in remaining ingredients except lemon zest.
Cook over medium heat, stirring constantly until thickened and coats back of spoon.
Pour into a strainer and press with back of spoon until coarse residue remains. Discard.
Stir in lemon zest. Cover surface with a piece of wax paper or plastic wrap and cool. Store in the refrigerator for up to 5 days.

Makes 1 1/4 cups