Baked Blueberry Slab Pie

Make the crust: In a food processor, combine the flour, granulated sugar, and salt and pulse a few times until blended. Add the cold butter and pulse until the mixture resembles coarse meal, about 10 pulses. Add 8 tablespoons of ice water and pulse 2-3 times to incorporate. The dough should hold together when squeezed between your fingers, but should not be sticky. If it is crumbly, add more water, 1 tablespoon at a time, pulsing twice after each addition.

Turn the dough out onto a clean surface and use your hands to bring together. There should be visible chunks of butter. Divide the dough in half and shape each half into a rectangle. Wrap the rectangles separately in plastic wrap and refrigerate for at least 2 hours, or up to overnight. Let the dough sit at room temperature for 30 minutes before rolling out.

Make the filling: In a large bowl, toss together the blueberries, granulated sugar, cornstarch, lemon zest, vanilla, and salt. Let sit while you roll out the dough.

On a lightly floured surface, roll out one dough portion into a 22 x 18-inch rectangle, about 1/8 inch thick. Wrap the dough around the rolling pin, then unroll it on top of a rimmed 13 x 18-inch baking sheet. Gently press the dough against the bottom and sides of the pan. Trim the edges with scissors or a knife, leaving a 1/2-inch overhang. Refrigerate while rolling out the dough for the lattice crust.

Roll out the remaining dough into a 22 x 18-inch rectangle. Use a ruler to mark 6 1-inch-wide spaces along the short side of the dough. With a fluted pastry roller, a pizza cutter, or a knife, cut six 1 x 22-inch strips from the dough. Gather up the scraps and re-roll the dough into an 18-inch square. Again, mark 1-inch-wide spaces along the dough and cut six 1 x 18-inch strips from the dough. (You'll use 5 of each size strip for the lattice, but will have an extra in case one breaks). If the dough becomes too warm as you work, refrigerate to firm up before continuing.

Pour the blueberry filling into the chilled bottom crust and spread evenly. Place 5 of the longer strips lengthwise across the pie, spacing evenly. Fold back every other strip halfway and lay a short strip perpendicularly across the unfolded strips. Repeat to place 4 more short strips evenly across the pie, folding back the alternate long strips as needed. Trim any overhanging lattice strips, then pinch together the strips and overhanging bottom crust around the edges of the baking sheet.

In a small bowl, beat together the egg and room temperature water. Brush the egg wash over the lattice crust, then sprinkle with the coarse sugar. If the dough is very warm, refrigerate for 10 minutes before baking.

When ready to cook, set the Traeger temperature to 400°F and preheat with the lid closed for 15 minutes.

Place baking sheet on the grill grate, close the lid, and bake until the crust is golden and the filling is bubbling, about 45 minutes, tenting the pie with aluminum foil if the top is browning too quickly.

Transfer the baking sheet to a wire rack and let the pie cool for at least 1 hour before slicing and serving. Enjoy! Note: The pie can be baked up to 1 day ahead; let cool completely, then cover with foil and let stand at room temperature.