Shape the pie crust into a disc, and on a lightly floured surface, roll it out into about a 12-inch circle. Drape over a 10-inch tart pan with a removable bottom, and gently press it in to fit into the bottom and sides. Use the rolling pin to roll across the edge of the pan to cut the pastry cleanly away; discard any scraps.
Review my How to blind bake a pie crust tutorial. Place a piece of foil or parchment in the pastry and fill with pie weights; bake for 15 minutes, then remove the weights and foil and bake for another 10 minutes, or until golden. Remove and set aside to cool completely.
Make the Cranberry Clementine Curd: In a medium saucepan, combine the cranberries, 1 cup + 3 Tablespoons of sugar, cardamom, clementine zest and juice. Bring to a simmer over medium heat. Cook for 10 minutes, until the berries pop and soften.
Set a fine-mesh colander over a bowl and pour in the sauce; press down firmly with the back of a ladle on the solids to extract as much cranberry juice and puree as possible. Discard the solids in the sieve.
Stir the butter into the cranberry sauce, one cube at a time, until it is all melted and incorporated. Mixture will be quite cool.
Beat eggs and egg yolks lightly in a separate bowl. Slowly whisk a cup of the cranberry liquid into the eggs, tempering them. Pour egg mixture into the rest of the cranberry liquid and whisk to combine. Return liquid to the saucepan, and cook over low heat, whisking constantly, until it bubbles and thickens enough to coat the back of a spoon.
Strain the curd one final time through a fine-mesh sieve into another bowl, using the back of a ladle to push it gently through.
Scrape the cranberry curd into the pre-baked tart shell and use an offset spatula to smooth the top.
Let stand at room temperature until set, about an hour. Refrigerate for one hour and up to 24 hours.
For the Eton Mess Topping: Whip the cream and 1 Tablespoon of sugar together until soft peaks form. Crumble in the meringues by hand, leaving some chunks big and other tiny. Fold in most of the candied kumquats.
Mound the Eton mess onto the cranberry curd tart. Crumble a few more meringues on top and garlish with remaining candies kumquats. Serve at once.
Alternatively, cranberry tart can be stored up to two days, refrigerated, just note that the meringues will soften in the whipped cream topping.