How to Make It
Make the dough: Pulse together flour, sugar, and salt in a food processor until combined, 5 to 6 times. Add butter; pulse until most of the butter is pea-size, about 20 times. While pulsing, drizzle in ¼ to ½ cup ice water until dough just holds together when squeezed. Turn dough out onto a large sheet of plastic wrap; pull in edges of wrap to gather dough, using your knuckles to press dough into a disk. Wrap tightly. Refrigerate for at least 2 hours and up to 3 days (or freeze for up to 1 month).
Prepare the filling: Toss together apples, butter, sugar, honey, lemon zest, lemon juice, and salt in a large bowl.
Assemble the galette: Roll out chilled dough into an 18-inch round on a lightly floured surface. Transfer to a parchment-lined baking sheet (dough will hang over edges at first). Process pistachios, sugar, and salt in a food processor until finely ground, 30 to 45 seconds. Sprinkle half of the pistachio sugar over center of dough, leaving a 3-inch border.
Spread apple filling evenly over dough (keeping the 3-inch border). Fold edges of dough over filling, overlapping as needed. Transfer baking sheet to freezer until galette is firm, about 10 minutes.
Meanwhile, preheat oven to 350°F with rack in lowest position. Remove baking sheet from freezer and brush edges of galette with egg; sprinkle with remaining pistachio sugar. Bake until crust is deep golden brown and apples start to brown, 50 to 55 minutes. Let stand at room temperature for at least 10 minutes and up to 8 hours.
Less handling means tastier pastry, so make galette instead of pie. There's much less fussing with the dough.