- 6 large egg yolks
- 3/4 cup sugar
- Zest of 1 orange
- 1/4 cup plus 1 tablespoon freshly squeezed orange juice
- 2 tablespoons plus 1 1/2 teaspoons freshly squeezed lemon juice
- 1/8 teaspoon coarse salt
- 1/2 cup plus 2 tablespoons plus 1 1/2 teaspoons unsalted butter, cold, cut into small pieces
Combine yolks, sugar, orange zest, orange juice, and lemon juice in a heavy-bottomed saucepan; whisk to combine. Cook over medium-high heat, stirring constantly with a wooden spoon or heat-proof spatula (be sure to scrape sides of the pan), until the mixture is thick, 8 to 10 minutes. Let mixture come to a rapid simmer and cook, continually scraping sides of pan, for 2 minutes.
Remove saucepan from heat. Add salt and butter, one piece at a time, stirring until smooth. If desired, strain through a fine sieve into a medium bowl. Cover with plastic wrap, pressing it directly onto the surface of the curd to prevent a skin from forming. Refrigerate until chilled and very firm, at least 2 hours or up to 1 1/2 weeks.