Using a medium bowl, beat together the sugar, lemon zest, and butter until combined and creamy
Beat in the eggs, one at a time until combined and smooth
Beat in the egg yolks one at a time until combined and smooth
Beat in the lemon juice until combined
Pour the mixture into a large pot over medium to high heat and allow the mixture to simmer
Stir constantly for about 10 - 15 minutes or until the mixture starts to thicken to pudding-like
Remove and strain through a mesh strainer or cheesecloth
Spoon the lemon curd into the jars and allow to cool completely before placing the lids on and placing them into the fridge
Enjoy on toast, croissants, or thumbprint cookies!