Preheat the oven to 350 degrees.

Roll out the pie crust on a floured surface with a rolling pin, and using a round cookie cutter cut round circles out of the pie crust.

Place pie crust rounds in the muffin tin, and push gently into the tin to form a small crust.

Prick the bottom of the crusts lightly with a fork.

Bake at 350 degrees for 12 to 15 minutes or until light golden brown.

Remove from oven and loosen the small crusts from the muffin tin, move to a wire rack to cool slightly.

While crusts cool, whisk the egg yolks in a medium size bowl and set aside.

In a medium saucepan, combine cornstarch, water, sugar, and salt.

Stir constantly over medium low heat until mixture comes to a boil for one minute. Remove from heat.

Pour half of the mixture into the egg yolks in a thin stream, slowly and whisking constantly.

Pour the hot egg mixture back into the saucepan, still whisking constantly.

Return the pan to the heat, and cook on low for an additional 3 minutes, stirring constantly.

Remove from heat, and stir in lemon juice, and lemon zest.

Whisk in the butter one tablespoon at a time. Stirring occasionally while the filling cools.

When filling is cool, place the crusts back in the muffin tin and fill the crusts almost to the top with the lemon filling.

In the mixing bowl of a stand mixer, beat the egg whites until stiff peaks form.

Add the cream of tartar and salt, and gently beat in the sugar until glossy.

Fill a pastry bag with the meringue and top the filled pies with the meringue.

Place the pies back in the oven under the broiler until the meringue is a light golden brown.

Remove pies to a wire rack to cool. Serve, and enjoy!