Coconut Cupcakes with Lime Curd Filling

To make the lime curd, in the top pan of a double boiler or in a nonreactive saucepan, whisk together the eggs and granulated sugar until blended. Then whisk in the lime juice. Set the top pan over but not touching simmering water in the bottom pan, or set the saucepan over medium-low heat. (If using a saucepan, take care not to heat the mixture too quickly.) Cook, stirring constantly with a wooden spatula or spoon, until the mixture is warmed through, 1 to 2 minutes.

Begin adding the butter a little at a time, stirring each addition until blended before adding more. Continue cooking, stirring constantly and scraping the bottom of the pan, until a finger drawn across the back of the spatula leaves a path, 8 to 10 minutes more. Immediately remove the pan from the heat. Pass the curd through a chinois set over a nonreactive bowl and let cool to room temperature. Cover and refrigerate for at least 1 hour or up to 2 weeks.

To make the cupcakes, have all the ingredients at room temperature. Preheat an oven to 350°F. Line a 12-well muffin pan with cupcake papers.

In a large bowl, sift together the flour, baking powder and salt. Set aside.

In the bowl of an electric mixer fitted with the flat beater, beat the butter on high speed until creamy, about 30 seconds. Gradually add the granulated sugar and continue beating, occasionally scraping down the sides of the bowl, until light and fluffy, 4 to 5 minutes.

Reduce the speed to low and fold in the flour mixture in three additions, alternating with the milk and beginning and ending with the flour, until just blended. Stir in the vanilla and coconut extract.

In a large copper beating bowl or mixing bowl, beat the egg whites until stiff peaks form. Using a rubber spatula, fold 1/2 cup of the egg whites into the batter until smooth, then carefully fold in the remaining whites until smooth and blended. Divide the batter among the prepared wells.

Bake until the cupcakes are golden and a toothpick inserted into the center comes out clean, about 15 minutes. Transfer the pan to a wire rack and let cool for 10 minutes. Remove the cupcakes from the pan and let cool on the rack to room temperature.

Fit a pastry bag with a #2 tip and fill the bag halfway with the lime curd. Insert the tip into the top of each cupcake and squeeze the bag to fill the cupcake centers with the curd.

To make the glaze, in a bowl, combine the lime juice, confectioners sugar and rum, and whisk until smooth and blended. Brush the cupcakes with the glaze and sprinkle with the toasted coconut.