A classic lattice-top sour cherry pie with a flaky, tender rye crust.
To make the crust, whisk to combine flours, sugar, and sea salt. Use a large hole grater to grate in cold butter and then rub into flour mixture with your fingertips just until well combined. Use a silicone spatula to fold in 1/2 cup ice water, and then drizzle in just a tablespoon at a time until the dough holds together in a shaggy ball.*
In a large bowl, toss pitted** cherries with 1/2 cup sugar, ground tapioca, lemon zest, spices, and sea salt. Set aside at room temperature while you roll the crust.
On a lightly floured sheet of parchment, roll one of the chilled dough discs into a 12-inch circle. Press into a metal pie pan*** and trim all but 1-inch of the overhanging dough. Set pie pan in the freezer while you roll the lattice.
On the same surface, roll the second disc into a 10 x 15-inch rectangle. Use a sharp paring knife or pastry cutter to cut 6 (2-inch) wide strips. If needed, gather scraps and re-roll dough once (dough with become tough after that). Working quickly, spoon filling into chilled pie shell. Lay 3 dough strips parallel across pie. Weave in remaining 3 strips in the other direction.**** Trim any excess dough, fold bottom crust up around the edge, and crimp. Brush top of crust with egg and sprinkle with remaining 2 tablespoons sugar.
*If you're new to homemade pie crusts note that whole grains can be especially hard to work with. I find a wetter dough is easier to work with, so add enough water that it holds together easily. Make sure your dough is well chilled. Roll dough out on parchment paper, using as much flour as you need to roll it out easily. If things get at all gooey, just pause and put dough back in the fridge to chill for 10 minutes.
**A good cherry pitter makes fast work of cherry pitting – this OXO one is the best I've used.
***Metal pie pans make the transition from fridge to oven easier and safer, since glass or ceramic pans may shatter when going from the cold fridge to the hot oven.
****Lattice weaving tips here.