In a large mixing bowl, combine all-purpose flour, sugar, and salt. Toss in cold, cubed unsalted butter, and rub it into the dry ingredients until the mixture resembles walnut halves.

Gradually add cold water and apple cider vinegar, mixing until you can form the dough into a disc. Wrap in plastic and chill in the refrigerator for at least 2 hours.

Dust a clean surface with flour and roll the dough into a 12-inch circle, about ⅛ inch thick.

Transfer the rolled dough to a pie plate, gently pressing it into the corners and trimming excess dough.

Crimp the edges and place it back in the fridge to chill for another 15 minutes.

Preheat your oven to 400°F (200°C). Line the chilled pie crust with parchment paper, filling it with pie weights or dried beans.

Bake for 12-15 minutes until the edges are lightly golden. Remove from oven and take out the weights and parchment.

Lower the oven temperature to 375°F (190°C). In a mixing bowl, whisk together the apple butter, sweetened condensed milk, eggs, vanilla extract, and spices until smooth.

In a separate bowl, combine oats, sugar, flour, and cinnamon.

Add cold, cubed butter and rub it into the mixture until it forms clumps.

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

Crumble the oat topping generously over the top. Bake for 35-45 minutes, or until the topping is golden brown.

Allow the pie to cool at room temperature for about 30 minutes, then chill in the fridge for at least 2 hours before slicing.