Wash Limes: Rinse limes under running water. Optionally, soak in a baking soda solution for 15 minutes to remove pesticides.
Zest Limes: Peel the zest from one lime using a microplane or zester. Avoid discolored spots.
2 limes
Juice Limes: Squeeze out the juice from the limes into a pot.
Prep Eggs: Whisk eggs in a bowl, mix in half the sugar, and set aside.
2 eggs
Heat Juice: Combine lime zest, remaining sugar, and lime juice in the pot. Heat to boiling then remove from heat.
1/3 cup sugar
Temper Eggs: Gradually mix hot lime juice into eggs to prevent curdling, stirring constantly.
Cook Mixture: Return mixture to low heat. Stir continuously until it thickens.
Add Butter: Off heat, add butter and stir until melted and incorporated.
3 tablespoons unsalted butter
Cover: Place plastic wrap directly on the curd to avoid skin formation.
Cool & Chill: Let the curd cool, then refrigerate with plastic wrap on.