1. Preheat the oven to 350°F (175°C). Place the pie crust in a pie dish and bake for 10 minutes or until golden. Set aside to cool.

2. In a medium saucepan, whisk together the sugar, cornstarch, and salt. Gradually add water, stirring to combine.

3. Place the saucepan over medium heat and bring to a boil, whisking constantly. Once it thickens, reduce heat.

4. In a small bowl, whisk the egg yolks. Slowly add a few spoonfuls of the hot sugar mixture into the yolks, whisking constantly, then pour the yolk mixture back into the saucepan.

5. Cook for 2-3 minutes, whisking until thick. Remove from heat and stir in butter, lemon zest, lemon juice, and vanilla extract. Pour the lemon filling into the baked pie crust.

6. For the meringue, beat the egg whites with cream of tartar until soft peaks form. Gradually add the sugar, continuing to beat until stiff peaks form.

7. Spoon the meringue over the lemon filling, spreading it to the edges of the crust. Bake for 10-12 minutes or until the meringue is golden.

8. Allow the pie to cool for at least 1 hour before serving.