In a medium saucepan, add the fresh lemon juice, lemon zest, egg yolks, sugar, and pinch of salt. Heat over medium low heat.
1/2 cup Lemon juice, 1 TBSP Lemon zest, 4 Egg yolks, 3/4 cup White granulated sugar, Pinch of salt
Use a whisk and whisk constantly for 20-25 minutes. Heat the lemon curd until it starts to thicken. By 20 minutes, it will get foamy on top, this is another indication that it is ready. Whisk constantly otherwise, the egg yolks will scramble and curdle.
Once thickened, remove from heat and add the cold and cubed butter. Whisk until melted.
1/2 cup Unsalted butter
Once melted, pour into a container and place plastic wrap over the top. Chill in the fridge until cool. Once cool, store in an airtight container in the fridge.