In a saucepan, combine sugar, flour, and salt; gradually stir in milk.
Cook and stir over medium heat till mixture boils and thickens. Cook for 2 minutes and remove from heat.
Stir in small amount hot mixture into yolks; return to hot mixture and cook for 2 minutes stirring constantly.
Remove from heat, add butter, vanilla, and coconut, and cool to room temperature. To prevent a crust from forming, put clear plastic wrap or waxed paper directly on top, touching the surface of the hot pudding all the way to the sides of the bowl. After it is cool, pour into a 9-inch bakery shell.
Meringue
Preheat oven to 350. Beat the three egg whites with cream of tartar and vanilla till soft peaks form.
Gradually add in sugar, beating till all the sugar is dissolved and soft peaks form again.
Spread atop your pie, making sure to cover all your filling and "sealing" to the pastry crust, then sprinkle with your remaining flaked coconut.
Bake in oven for 12-15 minutes, or until meringue is golden. Cool then serve.