For the pastry:
- 1 1⁄4 cups all-purpose flour
- 1 Tbs. confectioners sugar
- Pinch of salt
- 8 Tbs. (1 stick) frozen unsalted butter, cut into
- 1 egg yolk
- 2 Tbs. ice water
For the filling:
- 1 1⁄2 cups sliced blanched almonds
- 3⁄4 cup plus 2 Tbs. granulated sugar
- 6 Tbs. (3/4 stick) unsalted butter, cut into
- 2 Tbs. all-purpose flour
- 1⁄4 cup almond liqueur
- 2 eggs
- 1 1⁄4 lb. purple plums, pitted and thinly sliced
Turn the dough out onto a lightly floured work surface and press into a disk. Roll out to fit a 10-inch tart pan with a removable bottom. Transfer the dough to the pan and trim even with the pan rim, pressing with your fingers so the dough adheres to the sides of the pan. Place the pan on a baking sheet and refrigerate while preparing the filling.
Preheat an oven to 400°F.
To make the filling, process the almonds in the food processor until finely ground. Add the 3/4 cup granulated sugar, 4 Tbs. (1/2 stick) of the butter, the flour and liqueur. Pulse until a paste forms. Add the eggs and process to incorporate.
Spread the filling in the dough-lined pan. Top with the plum slices, overlapping them in concentric circles and fitting them tightly together. Fill in the center with 2 rows of plum slices. Dot the plums with the remaining 2 Tbs. butter and sprinkle with the 2 Tbs. granulated sugar.
Bake until the top is brown, about 1 hour. Transfer to a wire rack and let cool. Remove the pan sides. Cut the tart into wedges and serve at room temperature.