Preheat your oven to 350°F (175°C).
Prepare the pie crust in a pie dish.
Arrange the sliced apples evenly over the pie crust.
In a mixing bowl, whisk together buttermilk, eggs, sugar, vanilla, cinnamon, nutmeg, and salt until well combined.
Pour the custard mixture over the apples in the pie crust.
Bake the pie for 45-50 minutes, until the custard is set and the top is slightly golden.
Let the pie cool before slicing.