from the SF Chronicle
Makes 2 cups
4 large eggs
1 cup sugar
Pinch of kosher salt
1/2 cup citrus juice
1 to 2 teaspoons of lemon juice (optional)
1/2 cup (4 ounces) unsalted butter, cut into small pieces
2 tablespoons citrus zest
Bring a medium pot of water to a gentle simmer over medium heat. Place a fine mesh strainer over a large stainless steel or heat-proof bowl. Set aside.
In another large stainless steel or heat-proof bowl, whisk together the eggs, sugar, salt and citrus juice until combined. (Mix in the optional lemon juice at this point.) Place the bowl so it rests above the simmering water, making sure the bottom of the bowl does not touch the water. Stir with a rubber spatula until the curd thickens, about 10 minutes.
Remove the curd from the heat and pour through the strainer. Dot the top of the strained curd with the butter and whisk until melted and combined. Stir in the zest. Cool slightly, then place a layer of plastic wrap directly on top of the curd to prevent a skin from forming. Chill in the refrigerator for at least one hour or up to overnight (the curd will continue to thicken as it chills).
The beauty of this recipe is that you can use whatever citrus you have on hand. Grapefuit, pomelo, oranges, lemons — the possibilities are endless. If using a sweeter fruit, like orange, add a teaspoon or two of lemon juice to balance out the tartness level.