Preparation for the tart shell: In a food processor, pulse together the flour, sugar, and salt. Add the butter and pulse until the mixture resembles coarse meal. Add the egg yolk mixture and pulse just until the dough can be gathered into a ball. Flatten into a 6-inch disc, wrap in plastic, and chill several hours or overnight. Let the dough soften slightly at room temperature before rolling.
On a lightly floured surface, roll the dough into a 13-inch round. Fit the dough into a 10 1/2-inch tart pan with a removable bottom. Trim the dough flush with the rim and freeze the tart shell until firm. Meanwhile, preheat the oven to 350 degrees F.
Line the shell with foil or parchment and fill with pie weights, rice, or dried beans. Bake for 20 minutes until set. Remove the foil and weights and bake an additional 10 to 15 minutes until lightly golden. Remove the shell from the oven and immediately brush the hot pastry with the egg white.
Hint: When rolling tart pastry, always save all the dough scraps in case you need them to repair a crack in a partially baked shell. If the pastry "bubbles up" during the baking process, gently prick the pastry with a fork to release air bubbles. Check several times and repeat if necessary. The egg white serves to seal the pastry, which is especially helpful with a liquid filling such as this. It is essential that there be no cracks or holes visible in the partially baked shell. Make any necessary repairs prior to filling.
Preparation for the tart: When the pastry is almost done baking, assemble the filling. Whisk together the eggs, sugar, orange juice, lemon juice, lemon zest and orange zest and cream till smooth. Transfer the tart shell to the oven. Place the filling in a pitcher and slowly pour into the shell as high as possible without overfilling. There might be a bit of filling left over.
Bake the tart for approximately 25 minutes, until the filling is barely set. Check the tart after 20 minutes and keep checking it every few minutes after that. It is crucial not to overbake this filling!
Cool to room temperature before serving with berries and whipped cream.
For serving: .
Recipe courtesy of Ben and Karen Barker's NOT AFRAID OF FLAVOR (University of North Carolina Press, 2001)