Preheat Oven:

Preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper or silicone baking mats.

Cream Butter and Sugar:

In a large bowl, beat the softened butter and 1 ½ cups of sugar together with an electric mixer until light and fluffy, about 2-3 minutes.

Add Eggs:

Beat in the eggs one at a time, ensuring they are fully incorporated before adding the next.

Mix Dry Ingredients:

In a separate bowl, whisk together the flour, cream of tartar, baking soda, and salt.

Combine Wet and Dry Ingredients:

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Prepare Cinnamon-Sugar Coating:

In a small bowl, combine ¼ cup sugar and 2 teaspoons cinnamon.

Shape and Coat Cookies:

Roll the dough into 1 ½-inch balls. Roll each ball in the cinnamon-sugar mixture until fully coated.

Bake:

Place the coated dough balls onto the prepared baking sheets, about 2 inches apart. Slightly flatten each ball with your hand or the back of a spoon. Bake for 8-10 minutes, or until the edges are set but the centers are still soft.

Cool:

Let the cookies cool on the baking sheet for 2-3 minutes, then transfer them to a wire rack to cool completely.