• Place a strainer over a medium-sized bowl, near the stove. Use a 2 or 3-quart non-reactive saucepan for this curd.
• Place the sugar in a medium-size bowl and zest the oranges directly into the sugar. Use your fingers to rub the orange zest into the sugar until the sugar turns orange and feels like wet sand.
• Juice the oranges. Place the juice in a 2 or 3-quart saucepan, bring it to a boil and then boil the juice until it’s reduced to 3/4 cup. Remove the pan from the heat and the let the orange juice cool for about 30 minutes or it is barely warm.
• Add the orange-sugar mixture, egg yolks, large eggs, and salt to the orange juice and whisk until the ingredients are well combined.
• Cook the mixture over medium heat, whisking constantly until the mixture is thickened and registers 185°F with an instant-read thermometer. It should coat the back of wooden spoon and leave a visible trail when you run your finger through it. When the mixture has thickened and reached temperature remove the saucepan from heat and whisk in the butter 1 tablespoon at a time.
• Pour the orange curd into the strainer and press it through the strainer with a spatula.
• Cover the surface of the curd with plastic wrap, gently pressing the plastic wrap onto the surface of the curd. Place the curd in the refrigerator and chill for at least 2 hours. Once the curd has chilled place it in an airtight container

Storage

• Store the curd in the refrigerator for up to 2 weeks. If any white spots appear on top of the curd discard it. It has started to mold.
• The curd can be frozen for up to 1 year in a freezer-safe container.