Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a medium bowl, whisk together the all-purpose flour, baking soda, and salt until well combined.

In a large mixing bowl, beat together the softened unsalted butter, granulated sugar, and brown sugar using an electric mixer on medium speed for 2-3 minutes.

Add the large egg and vanilla extract into the creamed butter mixture, mixing on low speed until well combined.

Gradually add the dry ingredients into the wet mixture, stirring gently until just combined.

Gently fold in the diced fresh peaches using a spatula.

Using a cookie scoop or tablespoon, drop rounded portions of dough onto the prepared baking sheets, leaving about 2 inches of space between each cookie.

In a small bowl, mix together the additional granulated sugar and ground cinnamon, and sprinkle it over the cookie dough.

Place the baking sheets in the oven and bake for 12-15 minutes, or until the edges are golden brown.

Once baked, let the cookies cool on the baking sheets for about 5 minutes before transferring them to a wire rack.