Preheat oven to 350°F (175°C).

In a saucepan over medium heat, combine the chopped apples, sugar, lemon juice, cinnamon, nutmeg, and water. Simmer for about 10-15 minutes, stirring occasionally, until the apples soften and form a compote-like consistency.

Remove from heat and let cool slightly. Stir in egg yolks and butter until well combined.

Pour the apple mixture into the pre-baked pastry shell and spread evenly.

In a clean, dry mixing bowl, beat the egg whites with cream of tartar until soft peaks form. Gradually add sugar while beating until stiff peaks form.

Spoon or pipe the meringue over the apple filling, ensuring it reaches the edges of the crust to seal.

Bake for 12-15 minutes, or until the meringue is golden brown.

Let cool before slicing and serving.