Preheat oven to 350 degrees Fahrenheit. Line 16 muffins cups with paper liners and set aside.
Cutting around the pit, section off one peach and cut it into thin slices. The remaining peaches should be pitted and diced, equaling about 1 cup once cut. Set aside.
In a large bowl, whisk together the sugar, flour, baking soda, salt, cinnamon, and ginger.
In another large bowl, whisk together the melted butter, eggs, and buttermilk.
Pour the wet mixture over the dry mixture and stir until just combined.
Add the diced peaches and chopped pecans and stir gently.
Using a large cookie scoop, portion out the batter, filling the muffin cups 3/4 full.
Arrange peach slices over the surface of the muffins.
Bake for 16-20 minutes, or until lightly browned on the edges and the middle springs back after gently touched.
Cool in muffin tins for 5 minutes, then remove to wire racks to cool completely.