Step 1

Preheat oven to 425 degrees F. Place pie crust in a 9-inch pie plate and flute edges; set aside.

Step 2

In a large bowl, whisk sugar, flour, and buttermilk. Add eggs, vanilla, and butter and whisk until thoroughly combined. Pour into pie shell; sprinkle evenly with cinnamon.

Step 3

Bake 10 minutes, then reduce oven to 325 degrees and continue baking 35 to 40 minutes, or until a knife inserted in center comes out dry.