Preheat your oven to 350°F (175°C). Grease and flour a standard 9x5 inch loaf pan, or line it with parchment paper.

In a large bowl, whisk together the flour, granulated sugar, baking powder, salt, and cinnamon until well combined.

In a separate medium bowl, whisk together the melted butter, eggs, milk, and vanilla extract until smooth. Pour the wet ingredients into the dry ingredients and mix with a spatula until just combined. Be careful not to overmix.

Gently fold in the diced fresh peaches until they are evenly distributed throughout the batter. Pour the batter into the prepared loaf pan and spread evenly.

Bake for 50 to 60 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean. If the top begins to brown too quickly, loosely tent the pan with aluminum foil after 40 minutes.

Remove the bread from the oven and let it cool in the pan for 15 minutes before carefully turning it out onto a wire rack to cool completely.

While the bread cools, prepare the glaze if desired: whisk together the powdered sugar, peach nectar/milk, and vanilla extract until smooth. Drizzle generously over the completely cooled bread before slicing and serving.