Using a food processor or mini-chopper, pulse the graham crackers until finely ground. In a medium bowl, combine the graham cracker crumbs, brown sugar and melted butter. Stir until fully combined.

Lightly butter or grease a 9x13” baking pan. Line the bottom of the pan with parchment paper. Press the crust mixture evenly into the bottom of the pan. (Tip: A flat-bottomed glass helps pack the crust mixture down evenly.)

Bake crust at 350°F for 15 minutes. Remove from oven and let cool.

Using a medium bowl, lightly beat the egg yolks; set aside. (Tip: Save the egg whites as they will be used for the meringue topping later!)

Using a medium saucepan, combine sugar, cornstarch, water, lemon juice and lemon zest.

Place saucepan over medium-high heat and bring mixture to a boil. Once boiling, remove from heat and very gradually stir about ½ cup of mixture into the bowl with the egg yolks. (Note: Add just 1-2 Tbsp of the mixture into the egg yolks at a time, stirring well after each addition.)

Transfer egg yolk mixture into the saucepan with the remaining lemon juice mixture; whisk until well combined. Bring mixture to a boil over medium-high heat, stirring constantly. Once mixture begins to boil, cook for 1 more minute, stirring constantly.

Remove saucepan from heat and stir in butter. Pour filling over cooked graham cracker crust.

Using a medium bowl, combine the egg whites, cream of tartar and vanilla. Using an electric mixer, whip mixture until foamy. (Tip: The egg whites will be easier to whip if you let them come to room temperature first.)

Gradually add the sugar and continue whipping until meringue is stiff and glossy.

Spread the meringue on top of the lemon filling.

Dust top of meringue lightly with powdered sugar before baking.

Bake at 350°F for 16-18 minutes, or until top of meringue turns light golden brown. Allow bars to cool to room temperature and then cover lightly and place it in the refrigerator.

Once chilled, slice into squares; serve chilled.