In a medium bowl, whisk together all dry ingredients (except sugar substitute) until well combined, set aside.

Add egg and vanilla, continue beating until egg is fully incorporated and mixture is once again smooth and fluffy.

With mixer turned down to low speed, slowly add dry ingredients mix to the mixing bowl of wet ingredients, and carefully mix until well incorporated and smooth.

Wrap dough ball in plastic film, chill for 1 hour. This is an important step for any gluten free cookie dough, don’t skip it!

Peel and finely dice the apples. I like small pieces, about ¼" cubes (roughly).

In a medium pot, melt the butter over medium heat. Add the chopped apple to the pot, cook until it starts releasing the juice, about 4-5 minutes.

As the apples are cooking, combine brown sugar substitute, xanthan gum, cinnamon, nutmeg, and salt in a small bowl.

Add dry mixture to the apples, toss to coat. Simmer on low for another 5 minutes or so, until the juice forms a thick glaze.

Remove from heat, stir in vanilla, and allow to cool to room temperature.

Line 2 cookie sheets with parchment paper.

Roll chilled cookie dough into balls that are about 1.5" in diameter, and place them on cookie sheets – leave about 2" between the cookies.

Gently use your thumb to press down in the middle of each cookie, making an indentation. Roll thumb slightly to stretch the indentation out a little.

Fill each indentation with about a teaspoon of apple pie filling, then chill cookies for at least another 30 minutes before baking.

Preheat oven to 350 F (180 C).

Allow to cool on sheets for 5 minutes or so, before gently transferring to baking rack or counter to finish cooling.

Once completely cool store in an airtight container until serving.