Blueberry Buttermilk Pie

With orange zest and real-deal vanilla seeds, the filling of this custardy pie tastes like the best blueberry pancake. Don't throw the vanilla bean away once you've scraped the seeds from it, though - that stuff is gold in the kitchen. Parbaking the crust of this blueberry pancake flavoured custard pie ensures the bottom will be crisp when it's done.

Pastry Crust:
¼ cup sugar
1 Tbsp. apple cider vinegar
3½ cups all-purpose flour, unbleached
1¼ cups (2½ sticks) unsalted butter, chilled, cut into 1" pieces
¾ tsp. kosher salt

Filling:
½ cup all-purpose flour, unbleached
2 Tbsp. fine grind cornmeal
½ tsp. kosher salt
1 cup sugar
½ cup + 2 Tbsp. unsalted butter, room temperature
2 tsp. orange zest, finely grated
1 vanilla bean, split lengthwise
4 large eggs, room temperature
1¼ cups buttermilk, room temperature
2 cups fresh (or frozen, thawed) blueberries

Make the Pastry Crust:
Stir sugar, vinegar, and 2 Tbsp. hot water in a small measuring glass to dissolve sugar. Add 1/3 cup ice water and stir to melt ice; chill in freezer until very cold, about 10 minutes (do not let it freeze).

Pulse flour, butter, and salt in a food processor until largest pieces of butter are pea size. Turn out onto a work surface and, using the heel of your hand, smash butter into flour to flatten. Working quickly, continue smashing butter into flour until mixture is pale yellow and resembles coarse meal. Gather into a mound and make a well in the center. Pour in sugar mixture, using your fingertips to slowly incorporate into flour; work in until only a few dry spots remain. Knead until no dry spots remain and dough holds together when pressed.

Divide dough in half, flatten into disks, and wrap each in plastic. Chill until firm, at least 2 hours.

Do Ahead: Dough can be made 3 days ahead. Keep chilled, or freeze up to 1 month.

Roll out pie dough on a lightly floured work surface to a 13" round about 1/8" thick. Transfer dough to a 9" pie dish and allow dough to slump down into dish, leaving about 2" overhang. Fold edges under and crimp all the way around, making sure dough extends to the outer edge of the lip of the pie dish (this will create a shelf for the dough to sit on, preventing it from sliding back into dish). Chill in freezer until dough is very cold, about 20 minutes.

Preheat an oven to 350°F (180°C/160°C fan, Gas Mark 4). Place a rack in middle of oven. Line pie dough with parchment paper or heavy-duty foil, leaving a 1½" overhang, and fill with pie weights or dried beans.

Bake until crust is golden around the edge, 20-25 minutes. Remove from oven and lift out parchment and pie weights and bake until surface of crust looks dry and is golden, 10-15 minutes longer. Transfer to a wire rack and let cool.

Meanwhile, reduce oven temperature to 325°F (165°C/140°C fan, Gas Mark 3).

Whisk cornmeal, salt, and ½ cup flour in a small bowl. Combine sugar, butter, and orange zest in a large bowl and scrape in vanilla seeds; reserve pod for another use. Using an electric mixer on medium speed, beat until light and fluffy, about 4 minutes. Add eggs one at a time, beating to blend after each addition and occasionally scraping down sides and bottom of bowl. Beat until well blended. Reduce speed to low and add dry ingredients; beat just to combine. With motor running, gradually add buttermilk; beat just to combine (mixture may look broken, which is okay). Using a rubber spatula, gently fold in blueberries. Scrape filling into cooled pie crust just to fill to crust edge (you might have some left over).

Bake pie until filling is puffed and golden and center wobbles slightly when jostled, 50-60 minutes. Transfer dish to a wire rack and let pie cool before slicing, at least 2 hours.

Makes 10 servings.

Make Ahead: Pie can be baked 1 day ahead. Store loosely covered at room temperature.