Make the pie dough:
In a large bowl, sift all-purpose flour, salt, and sugar together. Grate frozen butter and add into the flour mixture. Mix well so that the butter bits are covered in flour. Slowly add ice water into the flour and butter mixture, just enough to bring the dough together.
Turn dough out onto work surface and mix, making sure you don’t overwork your dough. Shape into a round and divide 2/3, then shape each into disks. Cover with plastic wrap and place in fridge to rest for about 30 minutes.
Fire up your Cru oven.
Make the pie filling.
In a large bowl, put the cubed pears, sugar, apple cider vinegar, vanilla, cinnamon, ground ginger, and corn starch. Mix thoroughly.
Take dough out of fridge and roll the larger piece into a circle. Gently place into a 8” cast-iron skillet or comparable vessel that can be used for a wood-fired oven. Pour pear filling mixture into the pie shell, spreading it out to make sure the entire bottom is covered. Dot the filling with butter.
Roll out the smaller dough into a circle and cover the filling, making sure the lid overhangs and completely covers the bottom. Seal the sides so that the filling doesn’t leak onto the oven floor. Poke holes on the lid for the steam.
Once you have built a sufficient fire, putting the embers onto the back or side of your oven, and the temperature is at about 500°F to 600°F, put the pie into the Cru oven to cook. Rotate every 10 minutes for even cooking. At 40 minutes, check your pie. VERY gently nudge one of the sides to see if the exterior is sufficiently browned. If so, pull the pie and let cool on a rack, if not, cook for another 5-10 minutes.
Let the pie cool for about an hour before slicing into it.