Coconut Macaroon Thumbprints with Key Lime Curd

To prepare lime curd: Whisk egg, egg yolks, lime juice and sugar in a small saucepan until combined. Place over medium-low heat and cook, stirring constantly with a wooden spoon, until the mixture starts to steam. Stir in butter one piece at a time, letting each piece melt before adding the next. Cook, stirring constantly, until all the butter is added and the mixture is very gently bubbling and thick enough to coat the back of the spoon, 3 to 5 minutes total. Pour the curd through a fine-mesh sieve into a small bowl to strain out any lumps; stir in lime zest.

Press a piece of plastic wrap directly on the surface of the curd to keep a skin from forming. Refrigerate until completely cold, about 2 hours.

To prepare macaroons: Preheat oven to 300 degrees F. Line a large baking sheet with parchment paper or a nonstick baking mat.

Combine 1/2 cup sugar, coconut, egg whites, vanilla and salt in a large bowl.

Drop 1-tablespoon mounds of dough on the prepared baking sheet, about 1 inch apart. Wet your finger or thumb with cold water and press in the center of each cookie to make an indentation.

Bake, rotating the pan front to back halfway through, until the cookies are pale golden brown, about 20 minutes. Let cool for about 5 minutes on the pan, then transfer to a wire rack to cool completely. Repeat with the remaining batter.

Once the cookies are cool, fill the centers with about 1 teaspoon lime curd each.