Set your oven to 350°F (175°C) so it is perfectly hot when the dough is ready. Line your baking sheets with parchment paper to ensure the cookies do not stick or burn.

In your large mixing bowl, beat the softened butter and the 1 1/2 cups of sugar. Mix for three minutes until the mixture looks very pale, light, and fluffy.

Add the eggs one at a time, beating well after each addition to keep the batter smooth. Stir in the vanilla extract to add a wonderful and warm aroma to the cookie base.

In your second bowl, whisk together the flour, cream of tartar, baking soda, and fine salt. Make sure there are no large clumps so the cookies rise evenly in the oven.

Slowly add the dry flour mixture to the wet butter mixture while the mixer is on low. Mix until just combined so you do not make the cookies tough or too hard.

Use a rubber spatula to gently fold in the finely diced fresh apple pieces into the dough. Ensure the apple bits are spread evenly so every cookie gets a fruity and sweet bite.

In a small bowl, mix the 1/4 cup of sugar and the two tablespoons of ground cinnamon. This spicy and sweet mixture is what gives the snickerdoodle its famous and classic look.

Scoop a tablespoon of dough and roll it into a smooth ball using your clean hands. Roll each ball in the cinnamon sugar mixture until it is completely and evenly coated.

Place the balls on the sheets and bake for 10 to 12 minutes until the edges are set. The centers should still look slightly soft and puffed up when you take them out.

Let the cookies rest on the hot baking sheet for five minutes to finish setting up. Transfer them to a wire rack to cool completely before serving them to your family.