How to Make It
Combine flour and salt in a medium bowl. Cut butter with a pastry blender until pieces are pea-size. Sprinkle 1 tbsp. ice water over mixture; gently stir and toss with a fork. Repeat to add 4 to 6 more tbsp. ice water, 1 tbsp. at a time, until dough is evenly moistened and a pinch of it holds together. Gather into a disk, wrap airtight, and chill at least 2 hours or overnight.
Preheat oven to 400°. On a lightly floured work surface, roll dough into a 13-in. circle, using a floured rolling pin; occasionally slide a metal spatula under dough and re-flour underneath. Cut around edge of dough with a pastry wheel or knife to neaten. Lift dough to a baking sheet and chill about 15 minutes.
Combine 2/3 cup granulated sugar, the cornstarch, and spices in a medium bowl. If pluots are quite tart, add a few more tbsp. sugar to spice mixture. Stir in fruit until cornstarch is moistened, then spoon fruit onto pastry right away, leaving a 1 1/2 in. rim uncovered. Fold and pleat rim over fruit. Brush rim with water and sprinkle with coarse sugar.
Bake until filling bubbles and crust is browned, 40 to 45 minutes. Cool on pan on a rack at least 1 hour.
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