Preheat Oven and Prep Pan:
Set the oven to 350°F (175°C). Coat a muffin tin with grease or insert paper liners.Whisk Dry Ingredients Together:
In a big bowl, combine the flour, granulated sugar, brown sugar, baking powder, salt, and cinnamon with a whisk.Mix Wet Ingredients:
In a separate bowl, mix the melted butter, eggs, milk, and vanilla extract using a whisk.Combine Wet and Dry Mixtures:
Add the wet blend to the dry one and fold with a spatula until barely combined.Fold in Diced Peaches:
Incorporate the diced peaches by folding them gently into the batter.Fill Muffin Cups:
Portion the batter into the muffin cups, filling each to roughly two-thirds full.Bake Until Golden:
Bake for 18-20 minutes until the tops turn golden and a toothpick inserted in the center emerges clean.Cool Muffins in Pan:
Let the muffins sit in the pan for 5 minutes, then move them to a wire rack to cool fully.