Gâteau Breton

Ingredients

¾ cup/100 grams pitted prunes or dried apricots (about 16)
2 tablespoons/30 milliliters rum
2 ¼ cups plus 2 1/2 tablespoons/300 grams all-purpose flour
1 cup/200 grams superfine sugar
Large pinch flaky sea salt
8 ½ ounces/240 grams unsalted butter (2 sticks plus 1 tablespoon), diced, more for greasing pan
6 extra-large egg yolks

In a small pot over medium-high heat, combine prunes, rum and 2 tablespoons water. (Use 1 cup/240 milliliters water if using dried apricots.) Cook until most of the liquid has been absorbed (about 5 minutes for prunes, 10 to 15 for apricots). Use a fork to mash into a thick purée. Cover and chill.
In a food processor, pulse to combine flour, sugar and salt. Add butter and pulse until mixture resembles bread crumbs. Add 5 egg yolks and pulse until mixture comes together as a dough. Divide in half, form into disks, and wrap in plastic wrap. Chill at least 2 hours or until firm.
Heat oven to 350 degrees. Grease and line an 8-inch round cake pan with parchment paper. Between two sheets of parchment paper or plastic wrap, roll one of the dough halves into an 8-inch circle. Transfer dough to prepared cake pan, pressing into edges. Spread prune or apricot purée across dough, leaving 3/4 inch border around outside edge. Roll second piece of dough into an 8-inch circle, transfer to cake pan, press around outside edge to stick the pieces together and seal in fruit purée.
In a small bowl, combine remaining egg yolk with 1 teaspoon water and beat lightly. Brush over top of cake, then use a fork to score a crisscross pattern into the dough. Bake until golden brown, about 50 minutes (cover with foil if cake is browning too quickly). Cool in pan 15 minutes. Flip onto a plate, then invert onto a wire rack and let cool completely.