1. Preheat your oven to 350°F (175°C) and grease a 9×5-inch loaf pan or line it with parchment paper.

2. In a mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, cinnamon, and nutmeg.

3. In a separate bowl, whisk the melted butter, granulated sugar, and brown sugar until well combined. Then, add the eggs, vanilla extract, and sour cream or Greek yogurt, mixing until smooth.

4. Gradually add the dry ingredients to the wet ingredients, folding them in gently. Once just incorporated, fold in the diced peaches and any optional add-ins.

5. Pour the batter into the prepared loaf pan and bake for 50-60 minutes, or until a toothpick comes out clean.

6. Let it cool in the pan for 10 minutes before transferring to a wire rack to cool completely.