1. Preheat your oven to 350 F (175 C). Grease a 9×5-inch loaf pan with 1 tablespoon of melted butter or cooking spray. Lightly dust it with flour, tapping out any excess.

2. In a large mixing bowl, whisk together the all-purpose flour, 1/2 cup granulated sugar, baking powder, baking soda, and salt. Make sure there are no lumps and everything is evenly distributed.

3. In a separate medium bowl, whisk together the sourdough discard, milk, 1/4 cup melted butter, egg, and vanilla extract until well combined and smooth.

4. Pour the wet ingredient mixture into the dry ingredients. Stir gently with a spatula or wooden spoon until just combined. Do not overmix; a few small lumps are fine.

5. Gently fold in the diced peaches, distributing them evenly throughout the batter.

6. Pour the batter into your prepared loaf pan, spreading it evenly. In a small bowl, mix the remaining 2 tablespoons of granulated sugar with 1/2 teaspoon of ground cinnamon. Sprinkle this cinnamon-sugar mixture generously over the top of the batter.

7. Bake for 45-55 minutes, or until a wooden skewer or toothpick inserted into the center of the loaf comes out clean. The top should be golden brown, and the edges should be pulling slightly away from the pan.

8. Once baked, remove the loaf from the oven and let it cool in the pan for about 10-15 minutes. Then, carefully invert it onto a wire rack to cool completely before slicing and serving.