Vinegar Pie
["3 egg yolks, beaten", "1 c. sugar", "1/4 Tbsp. salt", "1 3/4 c. boiling water", "1/4 c. cider vinegar", "1/4 c. cornstarch", "1/4 c. cold water", "1 tsp. lemon extract", "1 baked pie shell", "meringue (made from 3 egg whites)"]
["Place the egg yolks in the top of double boiler.", "Add sugar and salt.", "Gradually add boiling water, stirring constantly.", "Add cider vinegar and cornstarch that has been dissolved in 1/4 cup cold water.", "Cook over boiling water until thick and smooth, about 12 minutes."]
["egg yolks", "sugar", "salt", "boiling water", "cider vinegar", "cornstarch", "cold water", "lemon extract", "shell", "meringue"]