Combine first 3 ingredients in a small bowl; cut in margarine with a pastry blender until mixture resembles coarse meal and is pale yellow. Sprinkle water, 1 teaspoon at a time, over surface of dough; toss with a fork until dry ingredients are moistened and mixture is crumbly. Shape into a ball.
Roll dough into a 6-inch circle between 2 sheets of heavy-duty plastic wrap. Place in freezer 10 minutes or until top sheet of plastic wrap can be removed easily. Invert and fit dough into a 4-inch pie pan coated with cooking spray; remove remaining sheet of plastic wrap. Fold edges under and flute, if desired. Prick bottom of crust with a fork. Bake at 425° for 7 to 8 minutes or until golden. Let cool on a wire rack.
Combine 2 tablespoons sugar and cornstarch in a small saucepan. Gradually stir in milk and egg substitute. Cook, stirring constantly, over medium-high heat until mixture comes to a boil. Boil 1 minute or until thickened. Remove from heat; stir in 2 teaspoons coconut and vanilla. Spoon filling into cooled pastry.
Beat egg white and cream of tartar at high speed of an electric mixer until foamy. Gradually add 1 tablespoon sugar, beating until stiff peaks form and sugar dissolves (2 to 4 minutes). Spread meringue mixture over coconut filling, sealing to edge of pastry. Sprinkle with remaining 1 teaspoon toasted coconut. Bake at 325° for 20 to 25 minutes or until golden.