In a large mixing bowl, combine all-purpose flour, granulated sugar, and kosher salt. Using a pastry cutter, cut in cold unsalted butter until the mixture resembles coarse crumbs. Gradually drizzle in cold water and apple cider vinegar, mixing gently until a dough forms. Shape the dough into a disk, wrap it in plastic, and refrigerate for 30 minutes to help it firm up.

Preheat your oven to 350°F (175°C). Roll out the chilled dough on a floured surface to fit your pie pan, about 1/8 inch thick. Place the rolled dough into the pan, pressing it into the edges. Use parchment paper and pie weights or dry beans to blind-bake the crust for 15-20 minutes, or until golden brown.

In a mixing bowl, whisk together the apple butter, sweetened condensed milk, eggs, pure vanilla extract, ground cinnamon, ground cloves, and ground nutmeg until smooth and well combined.

Pour the apple butter filling into the pre-baked crust, spreading it evenly with a spatula.

In a separate bowl, combine old-fashioned oats, light brown sugar, additional flour, and melted butter. Stir until the mixture is crumbly and well mixed.

Sprinkle the oat topping evenly over the apple butter filling in the pie. Return the pie to the oven and bake for an additional 30-40 minutes, or until the filling is set and the topping is golden brown.

Once fully baked, remove the pie from the oven and let it cool on a wire rack for at least 30 minutes.