In a large bowl, whisk together flour and salt. Cut in the cold butter using a pastry cutter or two knives until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
Combine ice water and vinegar, then sprinkle over the flour mixture one tablespoon at a time, stirring gently with a fork until the dough begins to form. Shape into a disk, wrap in plastic, and refrigerate for at least 30 minutes.
Preheat your oven to 375°F (190°C). Roll out the chilled dough on a floured surface to about 12 inches in diameter. Transfer to a 9-inch pie plate, trim excess, and crimp edges.
Line with parchment paper and fill with dried beans or pie weights. Bake for 15 minutes, then remove weights and parchment and bake for an additional 5 minutes until lightly golden. Let cool while preparing the filling.
In a medium saucepan, whisk together sugar, cornstarch, and salt. Gradually whisk in water until smooth. Cook over medium heat, stirring constantly, until mixture comes to a boil and thickens (about 5-7 minutes).
Reduce heat to low. Gradually whisk about 1/2 cup of the hot mixture into the beaten egg yolks to temper them, then pour the egg mixture back into the saucepan. Cook for 2 more minutes, stirring constantly.
Remove from heat and stir in lemon juice, zest, and butter until completely incorporated. The filling should coat the back of a spoon and be glossy and smooth. Pour hot filling into the pre-baked crust immediately.
In a clean, grease-free bowl, beat egg whites and cream of tartar with an electric mixer until soft peaks form.
Gradually add sugar, 1 tablespoon at a time, while continuing to beat. Add vanilla and salt, then beat until stiff, glossy peaks form and sugar has dissolved. Test by rubbing a small amount between your fingers – it should feel smooth, not grainy.
Spread the meringue over the hot filling, starting from the edges and working toward the center. Make sure to seal the meringue to the crust edges to prevent shrinking. Create decorative peaks with the back of a spoon.
Bake at 350°F (175°C) for 10-12 minutes until the meringue is golden. Watch carefully to avoid over-browning.
Allow the pie to cool on a wire rack for at least 3 hours at room temperature before refrigerating. For clean slices, dip a sharp knife in hot water and wipe dry between cuts.