Best Ever Lemon Pie
["1 deep 9-inch baked pie shell", "1 1/4 c. sugar", "6 Tbsp. cornstarch", "2 c. water", "1/2 c. fresh lemon juice", "3 eggs, separated", "3 Tbsp. butter", "1 1/2 tsp. lemon extract", "2 tsp. vinegar"]
["Mix sugar and cornstarch together in top of double boiler. Add water.", "Combine egg yolks with juice and beat.", "Add to sugar mixture and cook over boiling water for 25 minutes or until thick. Add lemon extract, butter and vinegar and stir thoroughly.", "Pour into pie shell and let cool.", "Cover with meringue and brown in oven."]
["shell", "sugar", "cornstarch", "water", "lemon juice", "eggs", "butter", "lemon extract", "vinegar"]