Start by gathering all your ingredients. Make sure to peel, core, and dice your apples. Also, set out your butter to soften, making the mixing process easier.

In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until smooth. This will take about 2-3 minutes on medium speed. Add the eggs one at a time, mixing well after each addition.

In another bowl, whisk together flour, cream of tartar, baking soda, salt, and cinnamon. Gradually add the dry ingredients to the wet mixture, stirring until combined. Make sure there are no dry spots in the dough.

In a medium bowl, mix diced apples, sugar, cinnamon, lemon juice, and cornstarch. Stir until the apples are well-coated. Set aside for a few minutes to let the juices mingle.

Preheat your oven to 350°F (175°C) while you shape the dough.

Using your hands, take a small scoop of the snickerdoodle dough and flatten it slightly. Place about a teaspoon of the apple filling in the center. Fold the dough over the filling and pinch to seal completely. Roll it into a ball gently.

In a shallow bowl, mix granulated sugar and cinnamon for the coating. Roll each ball in this mixture to fully coat.

Place the coated bites on a parchment-lined baking sheet, leaving some space between each one. This will help them bake evenly.

Bake in the preheated oven for 15-20 minutes. They should be lightly golden on the edges. Keep an eye on them towards the end to ensure they don’t over-bake.

Once baked, allow the bites to cool for a few minutes on the baking sheet. Transfer them to a wire rack to cool completely before serving.