01 - Combine flour and salt in a bowl. Cut in cold butter until mixture resembles coarse crumbs. Gradually add ice water, stirring until dough forms. Shape into a disk, wrap, and refrigerate for 30 minutes. Roll out dough on floured surface, fit into 9-inch pie dish. Trim and crimp edges. Line with parchment and fill with pie weights. Bake at 400°F for 15 minutes, remove weights, bake 10 more minutes. Allow to cool.
02 - Whisk sugar, cornstarch, and salt in a saucepan. Gradually stir in water, lemon juice, and zest. Cook over medium heat, stirring constantly until mixture thickens and bubbles. In a separate bowl, whisk egg yolks. Temper yolks by whisking in a spoonful of hot lemon mixture, then return to saucepan. Cook for 2 minutes while stirring continuously. Remove from heat and stir in butter. Pour filling into cooled crust.
03 - Beat egg whites and cream of tartar in a clean bowl until soft peaks form. Gradually add sugar while beating until stiff and glossy peaks form. Beat in vanilla extract. Spread meringue evenly over hot lemon filling, sealing edges to crust.
04 - Bake at 350°F for 15 to 18 minutes until meringue is golden brown. Cool completely at room temperature, then refrigerate for at least 1 hour before serving.