In a medium, heavy bottom sauce pot, combine 8 large egg yolks, lemon zest, 1/2 cup plus 2 tablespoons lemon juice, and 1 cup granulated sugar. Whisk to combine and cook over medium-high heat, stirring constantly until the mixture reaches a temperature of 160 (F). When the curd is ready, it should be able to coat the back of a spoon.