Prepare the piecrust.
In a medium saucepan, stir together the 1 cup sugar, cornstarch, and salt. Gradually stir in the half-and-half or light cream. Cook and stir over medium-high heat until the filling mixture is thickened and bubbly. Cook and stir for 2 minutes more. Remove the saucepan from the heat.
Place egg yolks in a small bowl and beat with a rotary beater or fork till combined. Gradually stir about 1 cup of the hot filling into yolks. Pour egg yolk mixture into hot filling. Bring to a gentle boil. Cook and stir for 2 minutes more. Remove from heat.
Stir in the 1/3 cup coconut, butter or margarine, coconut extract, and the 1/4 teaspoon vanilla. Keep the filling warm while preparing meringue.
In a large mixing bowl, stir together the egg whites, the 1/2 teaspoon vanilla, and cream of tartar. Beat the mixture with an electric mixer on medium speed for about 1 minute or until soft peaks form (tips curl). Gradually add the 6 tablespoons sugar, 1 tablespoon at a time, beating on high speed for about 4 minutes more or until meringue mixture forms stiff, glossy peaks (tips stand straight) and all of the sugar dissolves.
Pour warm filling into baked pastry shell. Spread meringue over warm filling and seal to edge of crust. If you like, sprinkle with toasted coconut.
Bake the meringue-topped pie in a 350 degree F oven for 15 minutes. Cool on a wire rack 1 hour. Chill for 3 to 6 hours before serving. Store the pie, covered, in the refrigerator. Makes 8 servings.