Chef Way Ludovic Augendre, executive pastry chef of the specialty food shop Fauchon in New York City, makes his Key lime tart with two layers: The bottom is an almond-based cream and the top is a puckery lime curd.
Easy Way Instead of using a tart pan, make the dessert in a baking dish, leaving out the almond layer, and slice it into bars.
9 tablespoons cold unsalted butter, cut into 1/2-inch pieces
In a food processor, pulse the almonds and the confectioners' sugar until finely ground. Add the butter and pulse until smooth. Pulse in the egg and vanilla. Add the flour and process until blended. Press the pastry evenly into an 8-by-11-inch glass baking dish, pressing it 1 inch up the side. Trim the edge to 3/4 inch and chill until firm, at least 1 hour.
Preheat the oven to 350°. Prick the pastry with a fork and bake for 25 minutes, or until golden. Let cool completely.
In a heatproof bowl set over a pan of simmering water, cook the eggs, sugar, lime juice and zest, whisking, until an instant-read thermometer registers 180°, about 7 minutes. Set the bowl into an ice water bath and stir until the temperature drops to 130°, about 3 minutes. Whisk in the butter. Let cool at room temperature for 1 hour.
Pour the lime curd over the pastry and refrigerate until firm, at least 6 hours or overnight. Cut into bars and serve.