In a food processor, combine all-purpose flour, granulated sugar, and salt. Gradually add cold unsalted butter, pulsing until the mixture resembles coarse crumbs. Then, add the egg and pulse until a dough forms. Shape the dough into a disc, wrap it in plastic, and chill in the refrigerator for at least 1 hour.

In a saucepan, combine fresh or frozen cranberries, granulated sugar for the filling, and orange juice. Cook over medium heat until the cranberries burst, about 5–7 minutes. Blend the mixture until smooth and strain it back into the pan. Stir in butter, cornstarch, and vanilla, and cook over low heat until combined and thickened.

Allow the cranberry mixture to cool for a few minutes before whisking the egg yolks in a separate bowl. Gradually mix a small amount of the warm cranberry mixture into the yolks while whisking constantly to prevent scrambling. Pour the yolk mixture back into the saucepan and mix well. Remove from heat and let it cool to room temperature.

Preheat your oven to 350°F (175°C). Roll the chilled dough out on a floured surface to ¼ inch thick, cut out circles, and fit them into the tart pans. Use a fork to poke holes in the bottom of each crust, line with parchment paper, fill with pie weights, and bake for 20 minutes or until lightly golden.

Once the crusts are cool, carefully remove them from the pans. Spoon the cranberry curd into each tart shell and chill the assembled tartlets in the refrigerator for at least 1 hour.