Preheat oven to 350F and line 1x12 cavities muffin tin with muffin liners.
In a medium bowl, sift the flour, baking powder, and salt. Set aside.
In a large bowl, mix sour cream with egg yolk and whisk for about 30 seconds until well combined.
Add the sugar and mix to incorporate, drizzle in the melted butter and whisk to incorporate.
Add the flour mix into the egg mix followed by the sliced peaches and mix just until the flour has fully incorporated. Do not over mix.
Divided the batter between the muffin liners and bake for 20-22 minutes or until a toothpick comes out clean from the center of the muffins.