In a large mixing bowl, combine all-purpose flour and kosher salt. Cut in cold unsalted butter until the mixture resembles pea-sized crumbs. Gradually add ice-cold water, stirring until a shaggy dough forms. Wrap the dough in plastic wrap and refrigerate for 1-2 hours.

After chilling, preheat your oven to 375°F. Roll out the chilled dough on a floured surface to fit your pie plate. Place the dough in the plate, trim the edges, and freeze for 20 minutes. Dock the crust with a fork, line with parchment paper, and fill with pie weights. Bake for 15 minutes, then remove weights and bake for an additional 5 minutes until lightly golden.

In a mixing bowl, whisk together apple butter, large eggs, dark brown sugar, and all-purpose flour until smooth. Slowly incorporate sweetened condensed milk while whisking to ensure a creamy consistency.

Lower the oven temperature to 325°F. Pour the filling into the pre-baked pie crust and bake for 30 minutes. Transfer the pie to the bottom rack and bake for an additional 10-15 minutes, until slightly jiggly but firm.

Once baked, remove the pie from the oven and let it cool on a wire rack for at least 3 hours.

In a medium mixing bowl, combine heavy whipping cream, powdered sugar, vanilla, and ground cinnamon. Whip until soft peaks form, being careful not to over-whip.

Spread the cinnamon whipped cream over the cooled pie. Optionally, swirl in a bit more apple butter before serving.