Best-Ever Apple Galette

Make basic pie dough, and let chill 2 hours.  Meanwhile, prep your fruit filling: Combine sliced apples, brown sugar, lemon juice, cinnamon, and a pinch of salt in a large bowl. Gently fold to coat apples. Preheat oven to 400° and line a medium baking sheet with parchment paper. On a lightly floured surface roll dough into a 12" circle about 1/8" thick. Transfer to prepared baking sheet. Arrange apple slices on top of dough, leaving a 1 1/2" border around the edge. Fold the edge nearest to you towards the center. Rotate sheet plan slightly and repeat, until all edges are folded towards fruit. Brush egg wash over crust and sprinkle with demerara sugar. Bake until crust is golden and fruit is tender, 40 to 45 minutes. Transfer to cooling rack and let cool completely before slicing.