3/4 c. butter
1 3/4 c. white sugar
1 tbsp. vanilla
4 eggs, slightly beaten
1 tbsp. + 1 1/2 tsp. cider vinegar

Combine butter and sugar in saucepan over medium heat. Cook, stirring until smooth. Remove from heat. Add eggs. Mix good. Stir in vinegar and vanilla, beat to blend. Pour in shell and bake 300 degrees for 50 minutes until tested with a toothpick.