Melt the butter in a large skillet over medium heat and add the sliced apples.
Toss the apples to coat them well with the melted butter.
Add both types of sugar, cinnamon, apple pie spice, and salt.
Let it simmer and cook for about 4-5 minutes until the apples start to soften.
In a measuring cup, mix the water, cornstarch, and apple cider vinegar until smooth and without lumps.
Pour this mixture over the softened apples and stir carefully.
Let it simmer again until the filling thickens and the apples are tender.
Allow the filling to cool before using it in your favorite 9-inch pie crust.
