In a food processor, pulse your sugar and lemon zest.
In a bowl whisk together your eggs, sugar and juice.
In a sauce pan melt your butter. Add your egg mixture and whisk continuously on low until the mixture is thick, pale, and bubbly (about 15 minutes).
Remove from heat and strain your mixture to make sure you get the smoothest curd.
Place curd in a bowl and place a piece of plastic wrap on top to prevent a skin from forming.
Chill curd in fridge for 1-2 hours. Serve cold.