Crust first! Combine the flour, salt, and sugar in a food processor. Pulse to combine. Add the cold butter and process until mixture in crumbly. Then slowly pour ice water over the mixture and process just until moistened. Do not over process. The goal is to keep the butter as cold as possible and you want there to be small chunks of butter in the dough. This will make the crust flaky and yummy!
Transfer the dough to a lightly floured surface to knead into a ball. Place the dough ball in the fridge for 20 minutes.
Preheat oven to 350 degrees.
Filling time! Peel, core and slice apples. You can cut the apples into cubes (1/4-1/2 inch cubes) or slice them into 1/8 inch slices. It's up to you. If you want to get fancy, do slices and fan them out as you build your galette.
Combine cut apples with sugar, vanilla, cinnamon, melted butter, and salt; toss to combine.
Line a larger rimmed cookie sheet with parchment paper
Pull dough out of the freezer. Place dough on a lightly floured surface. Use a rolling pin to roll out the dough into a rough 14-inch circle.
Transfer the dough circle to the parchment-lined cookie sheet.
Place filling in the center of your dough circle. Leave about three inches around the edge.
Fold the edge of dough over the filling. Remember, it doesn't have to be perfect. Making a galette is so forgiving.
Beat egg. Using a pastry brush, brush the egg over the dough. Then, sprinkle the turbinado sugar over the top.
Bake on the middle rack for 60 minutes. Apples should be soft and the crust a beautiful golden color.
After baking let the tart cool for about 30 minutes. You might have liquid leaking out - no worries! Let the bake rest on the cookie sheet then transfer it a serving board using spatulas.