How to Make It
In a food processor, combine the flour with the sugar and salt. Add the butter and pulse just until it is the size of peas. In a small bowl, whisk the egg with the ice water. Drizzle the egg mixture over the dough and pulse just until evenly moistened; do not let it form a ball. Turn the dough out onto a work surface, gather it together and shape into a disk. Wrap in plastic and refrigerate until firm, at least 30 minutes.
In a medium bowl, toss the rhubarb with 1/2 cup of the sugar; transfer to a strainer. Set it over the bowl and refrigerate overnight to drain.
Preheat the oven to 375°. On a lightly floured surface, roll out the pastry to a 14-inch round. Fit the pastry into a 10-inch tart pan with a removable bottom and trim the overhanging pastry.
Line the pastry with foil and fill with pie weights, dried beans or rice. Bake the tart shell in the lower third of the oven for about 20 minutes, or until the pastry is set. Carefully remove the foil and weights and bake the shell for about 10 minutes, or until cooked and the bottom is lightly golden.
Press on the rhubarb to extract as much liquid as possible. In a bowl, toss the rhubarb with 1/3 cup plus 1 tablespoon of the sugar. Spread the rhubarb in the shell and bake in the center of the oven for 15 minutes, or until the rhubarb is just tender.
In a medium bowl, whisk the cream with the egg yolks and 3 tablespoons of the sugar. Pour the custard over the rhubarb and bake in the lower third of the oven for about 20 minutes, or until set.
Increase the oven temperature to 425° and position a rack in the upper third of the oven. In a large bowl, using a handheld electric mixer, beat the egg whites with the salt until firm peaks form. Gradually add the remaining 1/4 cup of sugar, beating until the whites are stiff and glossy. Spread the meringue over the tart all the way to the side. Bake in the upper third of the oven for 5 minutes, or just until the meringue is lightly browned. Let the tart cool, then remove the ring, slide the tart onto a cake plate and serve.