French Meringue and Lemon Curd Tartlets

For the lemon curd:
Using a vegetable peeler, remove zest from lemons and place in bowl of a food processor. Add sugar and pulse until zest is finely chopped.

Beat butter and lemon-sugar mixture in bowl of an electric mixer on medium speed for 2 to 3 minutes, until light and fluffy. Add eggs, one at a time, blending well after each addition. Add lemon juice and salt and blend until smooth.

Transfer mixture to a medium saucepan and place over low heat. Cook for about 10 minutes, stirring constantly, until a candy thermometer registers 180°F. Remove from heat and transfer to a clean bowl. Cover with plastic wrap, pressing wrap directly onto surface of lemon curd to prevent a skin from forming. Chill in refrigerator for at least 2 hours, until thickened.

For the crust:
Whisk together flours and salt in a medium bowl. Beat butter and powdered sugar in the bowl of an electric mixer on medium speed for 2 to 3 minutes, until well combined. Add egg and egg yolk, one at a time, blending well after each addition. With mixer on low speed, add flour mixture in 2 additions, blending until just incorporated.

Transfer dough to a lightly floured work surface. Divide dough in half and shape each into a flat disk. Wrap in plastic wrap and chill in refrigerator for at least 1 hour, or overnight.

Preheat oven to 375°F. Transfer one disk of dough to a lightly floured work surface and divide into 5 equal pieces. Roll each piece into a 5-inch circle and press dough into individual 4-inch tart pans. Trim any excess dough from around edges and place tarts on a large rimmed baking sheet. Line tart shells with aluminum foil and fill with pie weights. Repeat with the remaining disk of dough.

Bake tartlets for 8 minutes. Remove foil and pie weights and bake for another 10 to 12 minutes, until golden brown all over. Remove from oven and let cool completely.

For the meringue:
Place egg whites, cream of tartar, and salt in the bowl of an electric mixer fitted with whisk attachment. Beat on medium speed for 2 to 3 minutes, until frothy. Increase mixer speed to medium-high and gradually add sugar, beating for another 2 to 3 minutes, until stiff, thick, and shiny.

To assemble, spoon lemon curd into cooled tart shells. Spread meringue over tops of tartlets and use a small offset spatula to create peaks in the meringue.