Sprinkle coconut in crust; set aside. Stir together sugar and cornstarch.
Place egg yolks in a medium heavy saucepan; whisk in sugar mixture and milk alternately until smooth.
Cook and stir over medium-high heat until boiling and thickened, about 10 to 15 minutes. Remove from heat and stir in vanilla; pour over coconut in crust.
For Meringue: In a deep bowl, beat egg whites with an electric mixer on high speed until soft peaks form. Reduce mixer to low speed; add cream of tartar.
Gradually beat in sugar, one tablespoon at a time; beat until stiff, glossy peaks form. Beat in vanilla. Spoon Meringue over hot filling, sealing carefully to edge of crust.
Bake at 325 degrees until meringue is lightly golden, 15 to 20 minutes.