Snickerdoodle Pie

I clipped this out of a magazine a few months back, but I can't remember from where. It is good served both warm or cold, although is very different each way.
Pie crust recipe of your choice

1/4 tsp cinnamon
1 Tbl sugar

4 Tbl butter, melted and cooled
1 1/2 cups buttermilk
4 large egg yolks
1/4 cup flour
1 tsp vanilla
1/4 tsp salt
1 cup sugar

• Put a pie crust in a 9" pie pan. Place in fridge to keep cool while preparing the filling.
• Mix cinnamon and 1 tbl sugar together.
• Place an oven rack in the bottom third of the oven. Preheat oven to 350 degrees. Line a baking sheet with foil and place on the low oven rack.
• In a large bowl whisk together the melted butter, buttermilk, egg yolks, flour, vanilla, salt, and 1 cup of sugar. Pour into chilled pie shell. Sprinkle with cinnamon sugar.
• Place on preheated baking sheet and bake for 20 minutes. Without opening the oven reduce the heat to 325 degrees and bake until pie is set, puffed and golden, 20-30 minutes longer.
• Let cool on a wire rack and serve, or refrigerate and serve cold.