Instructions

1. Fill the bottom pot of a double boiler with 2 to 3 inches of water. Place on high heat. After water begins to boil, reduce the heat to low.
2. Place egg yolks, granulated sugar, lemon zest and lemon juice into the top of the double boiler. Whisk until completely blended and continue to whisk and cook until the mixture becomes thick and clear.
3. Remove the pan from heat. Cut the butter into 8 pieces and stir each piece into the curd. The butter will melt from the heat of the curd. Pour curd into a jar or bowl. Place a piece of plastic wrap over top of curd. This prevents a skin from forming on the top. The curd will continue to thicken as it cools.