Preheat oven to 180ºC degrees. Beat the egg yolks until they are a pale yellow. Pour in the milk and cream of tartar at the same time and beat on medium speed of an electric mixer for 5 minutes. Add the lime juice and mix for 5 more minutes. You cannot over mix on this recipe. Pour mixture into a 23 cm graham cracker pie shell and place on a cookie sheet. Bake for 15 minutes or until the pie turns light in color. Refrigerate. For the topping Add ingredients to a saucepan and bring to a boil. Lower heat and simmer until sauce is a golden brown. Refrigerate until thick. Pour over the key lime pie before serving. This pie will keep in the refrigerator for 3 days.