Preheat the oven to 350 degrees. Spray a 9-inch pie pan with cooking spray.

Combine the graham cracker crumbs with 4 tablespoons sugar and the melted butter. Press the mixture into the prepared pie pan.

Whisk together the egg yolks, condensed milk, lemon zest, and ½ cup lemon juice and pour into the crust.

Whip the egg whites with 1 ½ teaspoons of lemon juice until foamy on high speed. Add 1/3 cup powdered sugar and beat until stiff peaks form. Spread the meringue over the top of the pie, making sure to get all the way to the edges of the crust and sealing it.

Bake for 15 – 20 minutes or until the meringue has nice brown peaks. Let cool and refrigerate for 3 hours or overnight.