Cinnamon-Swirl Apple Slab Pie

INGREDIENTS

3 tbsp

unbleached all-purpose flour, plus more for dusting

recipes Test Kitchen's Favorite Pate Brisee, each shaped into a rectangular disk

4 tbsp

unsalted butter, room temperature, plus 2 tablespoons, refrigerated and cut into small cubes

1/2 cup

packed light-brown sugar

1 tsp

ground cinnamon

1/2 tsp

kosher salt

4 lb

assorted apples, such as Jonagold, Cortland, Granny Smith, and Empire, peeled, cored, and cut into 1/4-inch slices

2 tbsp

fresh lemon juice

6 tbsp

granulated sugar

1 tsp

pure vanilla extract

large egg, lightly beaten

Fine sanding sugar, for sprinkling