For Crust: Mix graham cracker crumbs, melted butter, and 1/4 cup sugar in a small bowl. Press mixture evenly in the bottom and sides of a 9-inch pie pan. Bake at 375 degrees for 8-10 minutes. Cool on wire rack.

For Filling: Combine gelatin, 1/2 cup sugar, and salt in a medium saucepan. Stir in well-beaten egg yolks, water, lemon zest, and lemon juice. Cook and stir over medium heat until gelatin dissolves and mixture begins to thicken slightly and is bubbly.

Remove from heat. Chill to consistency of corn syrup, stirring occasionally.

Beat egg whites until soft peaks form. Gradually add the remaining 1/2 cup sugar, beating until stiff peaks form. Fold egg whites into lemon mixture. Spoon into graham cracker shell.

Chill for several hours before serving.

Garnish with lemon slices if desired.