1. Prepare Your Loaf Pan and Preheat Oven: Start by preheating your oven to 350 F (175 C). Lightly grease and flour a standard 9×5-inch loaf pan, or line it with parchment paper, leaving an overhang on the sides to easily lift the loaf out later. This prevents sticking and makes for easy removal.

2. Combine Wet Ingredients: In a large mixing bowl, whisk together the sourdough discard, 1/2 cup granulated sugar, melted butter, egg, and vanilla extract until the mixture is smooth and well combined. The discard will incorporate easily, adding its characteristic tang.

3. Mix Dry Ingredients: In a separate medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Ensure there are no lumps and all ingredients are evenly distributed. This step is crucial for even rising.

4. Combine Wet and Dry Mixtures: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix the batter; a few small lumps are perfectly fine. Overmixing can lead to a tough loaf.

5. Fold in Peaches: Gently fold in the diced peaches until they are evenly distributed throughout the batter. Try not to mash the peaches; you want distinct pieces in your finished loaf.

6. Transfer to Pan and Top: Pour the batter into your prepared loaf pan, spreading it evenly with a spatula. In a small bowl, mix the remaining 2 tablespoons of granulated sugar with the 1/4 teaspoon of ground cinnamon. Sprinkle this cinnamon-sugar mixture evenly over the top of the batter in the loaf pan. This creates a lovely, slightly crisp, and fragrant crust.

7. Bake the Loaf: Place the loaf pan in the preheated oven and bake for 45-50 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 slightly pulled away from the sides of the pan.

8. Cool Before Slicing: Once baked, remove the loaf from the oven and let it cool in the pan for about 10-15 minutes. Then, carefully lift it out of the pan using the parchment paper overhang (if used) or invert it onto a wire rack to cool completely before slicing. This cooling time allows the loaf to set properly and prevents it from crumbling when cut.