Pulse flour, sugar, salt, and cold cubed butter in a food processor until pea-sized crumbles form. Drizzle in ice water until dough just holds together. Shape into a disk, wrap in plastic, and chill for 30 minutes (or roll out store-bought pie dough).

In a large bowl, toss sliced apples with dark brown sugar, cornstarch, cinnamon, nutmeg, lemon juice, and vanilla extract until evenly coated.

Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper. Roll dough out on the parchment into a 12-inch circle.

Arrange spiced apple slices in concentric circles or fan them neatly in the center, leaving a 2-inch border around the edge.

Fold pastry edges up and over the apples, pleating every couple of inches. Brush crust with egg wash and sprinkle generously with turbinado sugar.

Bake for 32-35 minutes until the pastry is deep golden brown and the apples are bubbling and tender. Drizzle warm salted caramel sauce and flaky sea salt over top right before serving warm with vanilla ice cream.