Step 1

Place pie crust in a 9-inch pie plate, pressing crust firmly into plate, then flute edges. Bake according to package directions.

Step 2

Meanwhile, in a medium saucepan, combine 1-1/2 cups sugar, the cornstarch and salt; mix well. Whisk in lemon juice and water until combined. Whisk in egg yolks. Add boiling water and butter and bring to a boil over medium heat, stirring constantly. Boil 1 minute, then remove from heat and stir in lemon zest. Pour into pie crust.

Step 3

Preheat oven to 350 degrees F.

Step 4

In a medium bowl, with an electric mixer, beat egg whites with cream of tartar until soft peaks form. Add remaining 6 tablespoons sugar and continue beating until stiff peaks form. Spread meringue over pie filling, sealing to edges of crust.

Step 5

Bake 12 to 15 minutes, or until golden. Let cool 6 hours, then slice and serve. Store leftovers in refrigerator.