Preheat oven to 425°. On a lightly floured surface, roll dough to a 1/8-in.-thick circle; transfer to a 9-in. pie plate. Trim pastry to 1/2 in. beyond rim of plate; flute edge. Refrigerate 30 minutes.
Line unpricked pastry with a double thickness of foil. Fill with pie weights, dried beans or uncooked rice. Bake on a lower oven rack 20-25 minutes or until edges are golden brown. Remove foil and weights; bake 3-6 minutes longer or until bottom is golden brown. Cool on a wire rack. Reduce oven setting to 350°.
In a small heavy saucepan, mix sugar, cornstarch and salt. Whisk in milk. Cook and stir over medium heat until thickened and bubbly. Reduce heat to low; cook and stir 2 minutes longer. Remove from heat.
In a small bowl, whisk a small amount of hot mixture into egg yolks; return all to pan, whisking constantly. Bring to a gentle boil; cook and stir 2 minutes. Remove from heat. Gently stir in chopped coconut, butter and vanilla until butter is melted.
For meringue, in a small bowl, beat egg whites with cream of tartar on medium speed until foamy. Gradually add sugar, 1 tablespoon at a time, beating on high after each addition until sugar is dissolved. Continue beating until soft glossy peaks form.
Transfer hot filling to crust. Spread meringue evenly over filling, sealing to edge of crust. Sprinkle with flaked coconut. Bake 12-15 minutes or until the meringue is golden. Cool 1 hour on a wire rack. Refrigerate at least 3 hours before serving. Yield: 8 servings.