Line several large baking sheets with parchment paper. Preheat the oven to 375℉.

Whisk together the flour, salt & baking soda in a small bowl. Set aside.

In a large bowl, beat the butter and granulated sugar with a mixer on medium-high speed until pale and fluffy, about 4 minutes.

Reduce the speed to low. Add in the egg and vanilla extract. Mix until incorporated. Add the flour mixture a little at a time; mix until just combined. Add about 1/2 of the peaches along with the preserves. Beat until just combined.

Add the remaining peaches and, using a spatula or wooden spoon, gently fold them into the dough.

Using a 1-tablespoon cookie scoop, drop the dough onto the prepared baking sheets, spacing about 2 inches apart. Combine the sanding sugar and cinnamon. Sprinkle each cookie with about 1/8 teaspoon of the cinnamon-sugar mixture.

If not baking all of the cookies at once, refrigerate the dough between batches. You may find it helpful to refrigerate the dough for about an hour to firm up before scooping. The prepared dough can be refrigerated in an airtight container for up to 3 days before using.

Bake the cookies, rotating sheets halfway through, until golden brown and just set, for about 13 minutes. If you prefer more crispy edges, bake for a total of 15 minutes. They will be very soft & tender and will need to cool on the baking sheets for 5 minutes. Transfer the cookies to a wire rack to cool completely.

These cake cookies are best when enjoyed right away. If need be, store them loosely covered so they don't get soggy.