Preheat the oven to 350 degrees. Caramelize 1 cup of sugar by placing it in a medium iron skillet (or heavy bottomed skillet) over medium heat. Begin stirring with a wooden spoon. The sugar will come together in pieces the size of almonds. Continue to stir until the sugar becomes like syrup and is the color of caramel. Take your time with this step; don't rush it. While the sugar is heating up, put the remaining 1 cup of sugar, flour and salt in a large saucepan. Mix well, and gradually add the milk. Add the beaten eggs. Cook over low to medium heat until hot, stirring constantly.
Add the caramelized sugar to the milk, stirring quickly. Cook until thick, continuing to stir. Add the butter, and pour into the pie shell. Top with the meringue and bake for 8 to 10 minutes.
To make the Meringue Topping: Beat the egg whites and cream of tartar in the bowl of an electric mixer until soft peaks form. Gradually add the sugar, and continue beating until stiff. Spread the meringue on top of the pie and bake.