Preheat oven to 375. Whisk together flour, salt, and baking soda.
Beat butter and granulated sugar with a mixer on medium-high speed until pale and fluffy, about 4 minutes. Reduce speed to low. Beat in egg and vanilla. Add flour mixture, and beat until just combined. Add peaches and jam, and beat until just combined.
Using a 1 1/2-inch ice cream scoop or a tablespoon, drop dough onto baking sheets lined with parchment, spacing about 2 inches apart. (If not baking all of the cookies at once, refrigerate dough between batches; dough can be refrigerated in an airtight container for up to 2 days.) Combine sanding sugar and cinnamon. Sprinkle each cookie with 1/8 teaspoon cinnamon-sugar mixture.
Bake cookies, rotating sheets halfway through, until golden brown and just set, 11 to 13 minutes. Let cool on sheets for 5 minutes, and then transfer cookies to wire racks to cool completely.
These cookies are best the day they're baked. They will soften at the edges after a couple of days, but they'll still taste delicious.