Preheat oven to 300F. Cream butter and sugar until light and fluffy, adding 1/2 cup sugar at a time. Blend in vanilla. Add eggs, one at a time. Combine
flour and salt; add small amount at a time. Add buttermilk. Sprinkle pecans in bottom of pie crust; pour custard mix over the pecans and bake 1 hour 30 minutes at 300F. The top browns as it cooks. Best served at room temperature.