1. To make the clementine curd: In a medium heatproof bowl, whisk the egg yolks until smooth. Set aside.

2. In a small heavy saucepan, combine the cornstarch with just enough clementine juice to make a thin paste, stirring to dissolve. Add the remaining clementine and lemon juices, sugar, zest, butter and salt. Cook the mixture over medium-low heat for 1 to 2 minutes, stirring occasionally, until it just starts to thicken. Whisking vigorously, add a small amount of the warm juice mixture to the egg yolks. Add the remaining juice mixture in small increments, whisking to incorporate after each addition.

3. Return the combined mixture to the saucepan and reduce the heat to low. Whisk gently until the mixture thickens enough to heavily coat the back of a spoon. Transfer to a bowl, cover with plastic wrap directly on the surface and refrigerate while you make the cookies, or preferably overnight.

4. To make the cookies: Sift together the flour, baking powder and salt onto a large square of waxed paper; set aside.

5. Combine the butter and sugar in a large bowl. Using an electric mixer on medium speed or a wooden spoon, beat for several minutes until light and fluffy. Add the egg, zest and vanilla extract, mixing well. Stop to scrape down the sides of the bowl, and add the sifted dry ingredients in 3 increments, mixing well to incorporate after each addition. Add the cranberries, mixing just to combine. Divide the dough in half, and wrap both halves in plastic wrap, flattening them into disks. Chill for at least 1 hour.

6. Preheat the oven to 375F. Line several large baking sheets with parchment paper or silicone liners.

7. Working with 1 disk of dough at a time, place on a lightly floured work surface. Using a floured rolling pin, roll out the dough to a thickness of about 1/4 inch and cut with a floured 1 1/4- to 1 1/2-inch cookie cutter. Re-chill the dough if it becomes too soft to cut or to lift cleanly from the surface. Place the cookies at least 1 inch apart on the baking sheets. Bake about 8 minutes, or until the edges turn light golden. Transfer the cookies to a wire rack to cool completely.

8. To assemble: Transfer the chilled clementine curd to a pastry bag (or a heavy resealable plastic food storage bag with a 1/8-inch cut made across 1 corner). Pipe about 1/2 teaspoon of curd onto half of the cookies. Cover with the other half of the cookies. Dust the tops with confectioners' sugar, if desired.