Furr's Cafeteria Butter Chess Pie

2 cups sugar
2 tablespoons all-purpose flour
5 large eggs, lightly beaten
2/3 cup buttermilk
1/2 cup butter or margarine, melted
1 teaspoon vanilla extract
1 unbaked 9-inch pastry shell

Combine sugar and flour in a large bowl; add eggs and buttermilk, stirring until blended. Stir in butter and vanilla extract, and pour into unbaked pastry shell. Bake at 350 degrees F for 45 minutes or until set. Cool in a wire rack. Check for doneness after the minimum baking time by gently shaking the pie. The center should be set with a slight jiggle.