Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
In a large mixing bowl, beat softened butter and sugar until light and fluffy.
Add egg and vanilla extract and mix well.
Stir in sour cream or Greek yogurt.
Fold diced peaches gently into the wet mixture.
Gradually add dry ingredients and mix until just combined.
Scoop dough onto prepared baking sheet using a cookie scoop or spoon.
Bake for 10–12 minutes until edges are lightly golden and centers remain soft.
Cool completely before glazing if desired.
For glaze, whisk powdered sugar, peach juice or milk, and vanilla until smooth. Drizzle over cookies.
