Remove Cheddar Pie Dough disk from refrigerator and set on the counter at room temperature to soften while you prepare the filling.

Prepare the apple filling

Mix the apples, brown sugar, lemon juice, cinnamon, and salt together in a large bowl. Allow it to sit for at least 15 minutes so the juices from the apples start to release. 

Stir in the tapioca flour. This will help the juices thicken as the filling bakes.

Shape the Galette

Once the dough has softened just enough to leave a thumbprint indention in the top, it’s ready to roll. Lay out a sheet of parchment paper or a silicone baking mat and dust lightly with flour. Use a rolling pin to roll out the dough disk into a 12”-13”, ⅛” - ¼” thick, round directly onto the prepared parchment paper or mat.

Whisk the egg with 1 teaspoon of water to make the egg wash. Then, brush the surface of the rolled dough round lightly with the egg wash.

Use a slotted spoon to scoop the apples out of the bowl. Arrange fruit on top, leaving a 2” border around the rim. You can just pile the apple slices on or arrange them neatly if you prefer.

To shape, carefully lift the edge up and fold it back over the filling, allowing the dough to naturally pleat at around 2” intervals as you fold. It should pleat about 10 times as you work your way around.

Dot the filling with small, cold cubes of butter.

With the galette on the parchment paper, lift and slide the parchment sheet onto a pizza pan or rimmed baking sheet.

Chill the galette

If you really want to ensure your galette holds its shape, place the galette (while on the baking sheet) in your freezer for at least 15-20 minutes until it firms up. Then bake directly from the freezer. *You can also freeze the shaped galette at this stage and bake at a later date. Just keep in mind it may take a few additional minutes to bake through.

Bake

Adjust oven rack to lower-middle position and preheat oven to 400°F. *If using a Baking Steel, place it on the rack and allow it to preheat along with the oven. It needs to heat up for at least 30 minutes before baking. You want it rippin' hot so it can absorb and conduct all of that heat and create the crispiest galette crust.

Lightly brush the egg wash mixture over the exposed dough edge and sprinkle liberally with turbinado or sparkling sugar.

Place the galette, while on the baking sheet or pizza pan, directly on top of the Baking Steel. Bake for 45-55 minutes, rotating the pan halfway through. The crust should be a warm golden brown and the apples should be tender and jammy. *If the apples and crust are starting to burn or brown too much, carefully tent with foil and continue baking.