Step 1: Prepare the Pie Crust

1. Preheat oven to 375°F (190°C).
2. Line an unbaked pie crust with parchment paper and fill with pie weights or dried beans.
3. Blind bake for 15 minutes, then remove weights and bake for another 5-7 minutes until golden brown.
4. To prevent a soggy crust, brush with egg white and bake for 3 more minutes.

Step 2: Make the Lemon Filling

1. In a saucepan, whisk together sugar, cornstarch, and water over medium heat until thickened.
2. In a separate bowl, lightly beat the egg yolks, then slowly add a few spoonfuls of the hot mixture while whisking.
3. Return the mixture to the saucepan, cooking for 2 more minutes while stirring.
4. Remove from heat and stir in lemon juice, zest, and butter until smooth.
5. Pour the hot filling into the baked crust and smooth the surface.

Step 3: Make the Meringue

1. In a clean, dry bowl, beat egg whites and cream of tartar until soft peaks form.
2. Gradually add powdered sugar, one tablespoon at a time, beating until stiff, glossy peaks form.
3. Spread the meringue over the warm filling, ensuring it touches the crust edges to prevent shrinking.

Step 4: Bake the Pie

1. Preheat the oven to 350°F (175°C).
2. Bake for 10-15 minutes or until the meringue is golden brown.
3. Let the pie cool at room temperature for at least 2 hours before slicing.